Title: Data Collection in the Field, Response Error, and Questionnaire Screening
1Data Collection in the Field, Response Error, and
Questionnaire Screening
2Nonsampling Error in Marketing Research
- Nonsampling (administrative) error includes
- All types of nonresponse error
- Data gathering errors
- Data handling errors
- Data analysis errors
- Interpretation errors
3Possible Errors in Field Data Collection
- Field worker error errors committed by the
persons who administer the questionnaires - Respondent error errors committed on the part of
the respondent
4Nonsampling Errors Associated With Fieldwork
5Possible Errors in Field Data Collection Field-Wor
ker Errors Intentional
- Intentional field worker error errors committed
when a fieldworker willfully violates the data
collection requirements set forth by the
researcher - Interviewer cheating occurs when the interviewer
intentionally misrepresents respondents. May be
caused by unrealistic workload and/or poor
questionnaire - Leading respondents occurs when interviewer
influences respondents answers through wording,
voice inflection, or body language
6Possible Errors in Field Data Collection Field-Wor
ker Errors Unintentional
- Unintentional field worker error errors
committed when an interviewer believes he or she
is performing correctly - Interviewer personal characteristics occurs
because of the interviewers personal
characteristics such as accent, sex, and demeanor - Interviewer misunderstanding occurs when the
interviewer believes he or she knows how to
administer a survey but instead does it
incorrectly - Fatigue-related mistakes occur when interviewer
becomes tired
7Possible Errors in Field Data Collection Responden
t Errors Intentional
- Intentional respondent error errors committed
when there are respondents that willfully
misrepresent themselves in surveys - Falsehoods occur when respondents fail to tell
the truth in surveys - Nonresponse occurs when the prospective
respondent fails - to take part in a survey or
- to answer specific survey questions
- Refusals (respondent does not answer any
questions) vs. Termination (respondent answers at
least one question then stops)
8Possible Errors in Field Data Collection Responden
t Errors Intentional
- Refusals typically result from the topic of the
study or potential respondent lack of time,
energy or desire to participate - Terminations result from a poorly designed
questionnaire, questionnaire length, lack of time
or energy, and/or external interruption
9Possible Errors in Field Data Collection Responden
t Errors Unintentional
- Unintentional respondent error errors committed
when a respondent gives a response that is not
valid but that he or she believes is the truth
10Possible Errors in Field Data Collection Responden
t Errors Unintentionalcont.
- Respondent misunderstanding occurs when a
respondent gives an answer without comprehending
the question and/or the accompanying instructions - Guessing occurs when a respondent gives an
answer when he or she is uncertain of its
accuracy - Attention loss occurs when a respondents
interest in the survey wanes - Distractions (such as interruptions) may occur
while questionnaire administration takes place - Fatigue occurs when a respondent becomes tired
of participating in a survey
11How to Control Data Collection Errors
Types of Errors Control Mechanisms
Intentional Field Worker Errors
Cheating Good questionnaire, Reasonable work
expectation, Supervision, Random
checks Leading respondent Validation Unin
tentional Field Worker Errors Interviewer
Characteristics Selection and training of
interviewers Misunderstandings Orientation
sessions and role playing Fatigue Require
breaks and alternate surveys
12How to Control Data Collection Errorscont.
Types of Errors Control Mechanisms
Intentional Respondent Errors Assuring
anonymity and confidentiality Falsehoods Incen
tives Validation checks Third person
technique Assuring anonymity and
confidentiality Nonresponse Incentives Thi
rd person technique
13How to Control Data Collection Errorscont.
Types of Errors Control Mechanisms
Unintentional Respondent Errors
Well-drafted questionnaire Misunderstanding
s Direct Questions Do you understand?
Well-drafted questionnaire Guessing Response
options (e.g., unsure) Attention
loss Reversal of scale endpoints Distractions
Fatigue Prompters
14Data Collection Errors with Online Surveys
- Multiple submissions by the same respondent (not
able to identify such situations) - Bogus respondents and/or responses (fictitious
person, disguises or misrepresents self) - Misrepresentation of the population
(over-representing or under-representing segments
with/without online access and use)
15Nonresponse Error
- Nonresponse failure on the part of a prospective
respondent to take part in a survey or to answer
specific questions on the survey - Refusals to participate in survey
- Break-offs (terminations) during the interview
- Refusals to answer certain questions (item
omissions) - Completed interview must be defined (acceptable
levels of non-answered questions and types).
16Nonresponse Errorcont.
- Response rate enumerates the percentage of the
total sample with which the interviews were
completed - Refusals to participate in survey
- Break-offs (terminations) during the interview
- Refusals to answer certain questions (item
omissions)
17Nonresponse Errorcont.
CASRO response rate formula (not mathematically
correct)
18Reducing Nonresponse Error
- Mail surveys
- Advance notification
- Monetary incentives
- Follow-up mailings
- Telephone surveys
- Callback attempts
19Preliminary Questionnaire Screening
- Unsystematic (flip through questionnaire stack
and look at some) and systematic (random or
systematic sampling procedure to select) checks
of completed questionnaires - What to look for in questionnaire inspection
- Incomplete questionnaires?
- Nonresponses to specific questions?
- Yea- or nay-saying patterns (use scale extremes
only)? - Middle-of-the-road patterns (neutrals on all) ?
20Unreliable Responses
- Unreliable responses are found when conducting
questionnaire screening, and an inconsistent or
unreliable respondent may need to be eliminated
from the sample.
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22Determining the Sample Plan
23The Sample Plan is the process followed to select
units from the population to be used in the sample
24Basic Concepts in Samples and Sampling
- Population the entire group under study as
defined by research objectives. Sometimes called
the universe. - Researchers define populations in specific terms
such as heads of households, individual person
types, families, types of retail outlets, etc. - Population geographic location and time of study
are also considered.
25 26Basic Concepts in Samples and Samplingcont.
- Sampling error any error that occurs in a survey
because a sample is used (random error) - Sample frame a master list of the population
(total or partial) from which the sample will be
drawn - Sample frame error (SFE) the degree to which the
sample frame fails to account for all of the
defined units in the population (e.g a telephone
book listing does not contain unlisted numbers)
leading to sampling frame error.
27Basic Concepts in Samples and Samplingcont.
- Calculating sample frame error (SFE)
- Subtract the number of items on the sampling
list from the total number of items in the
population. -
- Take this number and divide it by the total
population. Multiply this decimal by 100 to
convert to percent (SFE must be expressed in ) - If the SFE was 40 this would mean that 40 of
the population was not in the sampling frame
28Reasons for Taking a Sample
- Practical considerations such as cost and
population size - Inability of researcher to analyze large
quantities of data potentially generated by a
census - Samples can produce sound results if proper rules
are followed for the draw
29Basic Sampling Classifications
- Probability samples ones in which members of the
population have a known chance (probability) of
being selected - Non-probability samples instances in which the
chances (probability) of selecting members from
the population are unknown
30Probability Sampling Methods Simple Random
Sampling
- Simple random sampling the probability of being
selected is known and equal for all members of
the population - Blind Draw Method (e.g. names placed in a hat
and then drawn randomly) - Random Numbers Method (all items in the sampling
frame given numbers, numbers then drawn using
table or computer program) - Advantages
- Known and equal chance of selection
- Easy method when there is an electronic database
31Probability Sampling Methods Simple Random
Sampling
- Disadvantages (Overcome with electronic
database) - Complete accounting of population needed
- Cumbersome to provide unique designations to
every population member - Very inefficient when applied to skewed
population distribution (over- and under-sampling
problems) this is not overcome with the use of
an electronic database)
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33Probability Sampling Methods Systematic Sampling
- Systematic sampling way to select a
probability-based sample from a directory or
list. This method is at times more efficient than
simple random sampling. - Sampling interval (SI) population list size (N)
divided by a pre-determined sample size (n) - How to draw
- calculate SI,
- select a number between 1 and SI randomly,
- go to this number as the starting point and the
item on the list here is the first in the sample,
- add SI to the position number of this item and
the new position will be the second sampled item,
- 5) continue this process until desired sample
size is reached.
34Probability Sampling Methods Systematic Sampling
- Advantages
- Known and equal chance of any of the SI
clusters being selected - Efficiency..do not need to designate (assign a
number to) every population member, just those
early on on the list (unless there is a very
large sampling frame). - Less expensivefaster than SRS
- Disadvantages
- Small loss in sampling precision
- Potential periodicity problems
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36Probability Sampling Methods Cluster Sampling
- Cluster sampling method by which the population
is divided into groups (clusters), any of which
can be considered a representative sample. - These clusters are mini-populations and therefore
are heterogeneous. - Once clusters are established a random draw is
done to select one (or more) clusters to
represent the population. - Area and systematic sampling (discussed earlier)
are two common methods. - Area sampling
37Probability Sampling Methods Cluster Sampling
- Advantages
- Economic efficiency faster and less expensive
than SRS - Does not require a list of all members of the
universe - Disadvantage
- Cluster specification errorthe more homogeneous
the cluster chosen, the more imprecise the sample
results
38Probability Sampling Methods Cluster Sampling
Area Method
- Drawing the area sample
- Divide the geo area into sectors (sub-areas) and
give them names/numbers, determine how many
sectors are to be sampled (typically a judgment
call), randomly select these sub-areas. Do
either a census or a systematic draw within each
area. - To determine the total geo area estimate add the
counts in the sub-areas together and multiply
this number by the ratio of the total number of
sub-areas divided by number of sub-areas.
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40A two-step area cluster sample (sampling several
clusters) is preferable to a one-step (selecting
only one cluster) sample unless the clusters are
homogeneous
41Probability Sampling Methods Stratified Sampling
- This method is used when the population
distribution of items is skewed. - It allows us to draw a more representative
sample. - Hence if there are more of certain type of item
in the population the sample has more of this
type and - if there are fewer of another type, there are
fewer in the sample.
42Probability Sampling Methods Stratified Sampling
- Stratified sampling the population is separated
into homogeneous groups/segments/strata and a
sample is taken from each. The results are then
combined to get the picture of the total
population. - Sample stratum size determination
- Proportional method (stratum share of total
sample is stratum share of total population) - Disproportionate method (variances among strata
affect sample size for each stratum)
43Probability Sampling Methods Stratified Sampling
- Advantage
- More accurate overall sample of skewed
populationsee next slide for WHY - Disadvantage
- More complex sampling plan requiring different
sample sizes for each stratum
44Why is Stratified Sampling more accurate when
there are skewed populations?
- The less the variance in a group, the smaller the
sample size it takes to produce a precise answer. - Why? If 99 of the population (low variance)
agreed on the choice of brand A, it would be easy
to make a precise estimate that the population
preferred brand A even with a small sample size. - But, if 33 chose brand A, and 23 chose B, and
so on (high variance) it would be difficult to
make a precise estimate of the populations
preferred brandit would take a larger sample
size.
45Why is Stratified Sampling more accurate when
there are skewed populations? Continued..
- Stratified sampling allows the researcher to
allocate a larger sample size to strata with more
variance and smaller sample size to strata with
less variance. Thus, for the same sample size,
more precision is achieved. - This is normally accomplished by disproportionate
sampling.
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47Non-probability Sampling Methods Convenience
Sampling Method
- Convenience samples samples drawn at the
convenience of the interviewer. People tend to
make the selection at familiar locations and to
choose respondents who are like themselves. - Error occurs
- in the form of members of the population who are
infrequent or non-users of that location and - who are not typical in the population
48Nonprobability Sampling Methods Judgment Sampling
Method
- Judgment samples samples that require a
judgment or an educated guess on the part of
the interviewer as to who should represent the
population. Also, judges (informed
individuals) may be asked to suggest who should
be in the sample. - Subjectivity enters in here, and certain members
of the population will have a smaller or no
chance of selection compared to others
49 Nonprobabilty Sampling Methods Referral and
Quota Sampling Methods
- Referral samples (snowball samples) samples
which require respondents to provide the names of
additional respondents - Members of the population who are less known,
disliked, or whose opinions conflict with the
respondent have a low probability of being
selected. - Quota samples samples that set a specific
number of certain types of individuals to be
interviewed - Often used to ensure that convenience samples
will have desired proportion of different
respondent classes
50Online Sampling Techniques
- Random online intercept sampling relies on a
random selection of Web site visitors - Invitation online sampling is when potential
respondents are alerted that they may fill out a
questionnaire that is hosted at a specific Web
site - Online panel sampling refers to consumer or
other respondent panels that are set up by
marketing research companies for the explicit
purpose of conducting online surveys with
representative samples
51Developing a Sample Plan
- Sample plan definite sequence of steps that the
researcher goes through in order to draw and
ultimately arrive at the final sample
52Developing a Sample Plan Six steps
- Step 1 Define the relevant population.
- Specify the descriptors, geographic locations,
and time for the sampling units. - Step 2 Obtain a population list, if possible
may only be some type of sample frame - List brokers, government units, customer lists,
competitors lists, association lists,
directories, etc.
53Developing a Sample Plan Six steps
- Step 2 (concluded)
- Incidence rate (occurrence of certain types in
the population, the lower the incidence the
larger the required list needed to draw sample
from)
54Developing a Sample Plan Six steps continued
- Step 3 Design the sample method (size and
method). - Determine specific sampling method to be used.
All necessary steps must be specified (sample
frame, n, recontacts, and replacements) - Step 4 Draw the sample.
- Select the sample unit and gain the information
55Developing a Sample Plan Six stepsconcluded
- Step 4 (Continued)
- Drop-down substitution
- Oversampling
- Resampling
- Step 5 Assess the sample.
- Sample validation compare sample profile with
population profile check non-responders - Step 6 Resample if necessary.
56Determining the Size of a Sample
57Sample Accuracy
- Sample accuracy refers to how close a random
samples statistic (e.g. mean, variance,
proportion) is to the populations value it
represents (mean, variance, proportion) - Important points
- Sample size is NOT related to representativeness
you could sample 20,000 persons walking by a
street corner and the results would still not
represent the city however, an n of 100 could be
right on.
58Sample Accuracy
- Important points
- Sample size, however, IS related to accuracy.
How close the sample statistic is to the actual
population parameter (e.g. sample mean vs.
population mean) is a function of sample size.
59Sample Size AXIOMS
To properly understand how to determine sample
size, it helps to understand the following AXIOMS
60Sample Size Axioms
- The only perfectly accurate sample is a census.
- A probability sample will always have some
inaccuracy (sample error). - The larger a probability sample is, the more
accurate it is (less sample error). - Probability sample accuracy (error) can be
calculated with a simple formula, and expressed
as a value.
61Sample Size Axiomscont.
- You can take any finding in the survey, replicate
the survey with the same probability sample plan
size, and you will be very likely to find the
same result within the range of the original
findings. - In almost all cases, the accuracy (sample error)
of a probability sample is independent of the
size of the population.
62Sample Size Axiomscont.
- A probability sample can be a very tiny
percentage of the population size and still be
very accurate (have little sample error). - The size of the probability sample depends on the
clients desired accuracy (acceptable sample
error) balanced against the cost of data
collection for that sample size.
63There is only one method of determining sample
size that allows the researcher to PREDETERMINE
the accuracy of the sample results
- The Confidence Interval Method of Determining
Sample Size
64The Confidence Interval Method of Determining
Sample Size Notion of Confidence Interval
- Confidence interval range whose endpoints define
a certain percentage of the responses to a
question - Central limit theorem a theory that holds that
values taken from repeated samples of a survey
within a population would look like a normal
curve. The mean of all sample means is the mean
of the population.
65The Confidence Interval Method of Determining
Sample Size
- Confidence interval approach applies the
concepts of accuracy, variability, and confidence
interval to create a correct sample size - Two types of error
- Nonsampling error pertains to all sources of
error other than sample selection method and
sample size - Sampling error involves sample selection and
sample sizethis is the error that we are
controlling through formulas - Sample error formula
66The Confidence Interval Method of Determining
Sample Size
- The relationship between sample size and sample
error
67The Confidence Interval Method of Determining
Sample Size - Proportions Variability
- Variability refers to how similar or dissimilar
responses are to a given question - P () share that have or are or will do
etc. - Q () 100-P, share of have nots or are
nots or wont dos etc. - N.B. The more variability in the population
being studied, the larger the sample size needed
to achieve stated accuracy level.
68With Nominal data (i.e. Yes, No), we can
conceptualize answer variability with bar
chartsthe highest variability is 50/50
69The Central Limit Theorem allows us to use the
logic of the Normal Curve Distribution
- Since 95 of samples drawn from a population will
fall within 1.96 x Sample error - (this logic is based upon our understanding of
the normal curve) - we can make the following statement .
70If we conducted our study over and over,
e.g.1,000 times, we would expect our result to
fall within a known range ( 1.96 s.d.s of the
mean). Based upon this, there are 95 chances in
100 that the true value of the universe statistic
(proportion, share, mean) falls within this
range!
71The Confidence Interval Method of Determining
Sample Size Normal Distribution
1.96 X s.d. defines the endpoints for 95 of the
distribution
72We also know that, given the amount of
variability in the population, the sample size
affects the size of the confidence interval as n
goes down the interval widens (more sloppy)
73So, what have we learned thus far?
- There is a relationship among
- the level of confidence we desire that our
results be repeated within some known range if we
were to conduct the study again, and - the variability (in responses) in the population
and - the amount of acceptable sample error (desired
accuracy) we wish to have and - the size of the sample.
74Sample Size Formula
- The formula requires that we
- (a.)specify the amount of confidence we wish to
have, - (b.) estimate the variance in the population, and
- (c.) specify the level of desired accuracy we
want. - When we specify the above, the formula tells us
what sample size we need to use.n
75Sample Size Formula - Proportion
- The sample size formula for estimating a
proportion (also called a percentage or share)
76Practical Considerations in Sample Size
Determination
- How to estimate variability (p and q shares) in
the population - Expect the worst case (p50 q50)
- Estimate variability results of previous
studies or conduct a pilot study
77Practical Considerations in Sample Size
Determination
- How to determine the amount of desired sample
error - Researchers should work with managers to make
this decision. How much error is the manager
willing to tolerate (less error more accuracy)?
- Convention is 5
- The more important the decision, the less should
be the acceptable level of the sample error
78Practical Considerations in Sample Size
Determination
- How to decide on the level of confidence desired
- Researchers should work with managers to make
this decision. The higher the desired confidence
level, the larger the sample size needed - Convention is 95 confidence level (z1.96
which is 1.96 s.d.s ) - The more important the decision, the more likely
the manager will want more confidence. For
example, a 99 confidence level has a z2.58.
79Example Estimating a Percentage (proportion or
share) in the PopulationWhat is the Required
Sample Size?
- Five years ago a survey showed that 42 of
consumers were aware of the companys brand
(Consumers were either aware or not aware) - After an intense ad campaign, management will
conduct another survey. They want to be 95
confident (95 chances in 100) that the survey
estimate will be within 5 of the true share of
aware consumers in the population. - What is n?
80Estimating a Percentage What is n?
Z1.96 (95 confidence) p42 (p, q and e must
be in the same units) q100 - p58 e
5 What is n?
81N374 What does this mean?
- It means that if we use a sample size of 374,
after the survey, we can say the following of
the results (Assume results show that 55 are
aware) - Our most likely estimate of the percentage of
consumers that are aware of our brand name is
55. In addition, we are 95 confident that the
true share of aware customers in the population
falls between 52.25 and 57.75. - Note that ( .05 x 55 2.75) !!!!
82Estimating a MeanThis requires a different
formula
Z is determined the same way (1.96 or 2.58) e is
expressed in terms of the units we are
estimating, i.e. if we are measuring attitudes
on a 1-7 scale, we may want our error to be no
more than .5 scale units. If we are estimating
dollars being paid for a product, we may want our
error to be no more than 3.00. S is a little
more difficult to estimate, but must be in same
units as e.
83Estimating s in the Formula to Determine the
Sample Size Required to Estimate a Mean
- Since we are estimating a mean, we can assume
that our data are either interval or ratio. When
we have interval or ratio data, the standard
deviation of the sample, s, may be used as a
measure of variance. - How to estimate s?
- Use standard deviation of the sample from a
previous study on the target population - Conduct a pilot study of a few members of the
target population and calculate s
84Example Estimating the Mean of a PopulationWhat
is the required sample size, n?
- Management wants to know customers level of
satisfaction with their service. They propose
conducting a survey and asking for satisfaction
on a scale from 1 to 10 (since there are 10
possible answers, the range 10). - Management wants to be 99 confident in the
results (99 chances in 100 that true value is
captured) and they do not want the allowed error
to be more than .5 scale points. - What is n?
85What is n?
- S 1.7 (from a pilot study), Z 2.58 (99
confidence), and - e .5 scale points
- What is n? It is 77. Assume the survey average
score was 7.3, what does this tell us? A 10 is
very satisfied and a 1 is not satisfied at all. - Answer Our most likely estimate of the level of
consumer satisfaction is 7.3 on a 10-point scale.
In addition, we are 99 confident that the true
level of satisfaction in our consumer population
falls between 6.8 and 7.8 on the scale.
86Other Methods of Sample Size Determination
- Arbitrary percentage rule of thumb sample size
- Arbitrary sample size approaches rely on
erroneous rules of thumb (e.g. n must be at
least 5 of the population). - Arbitrary sample sizes are simple and easy to
apply, but they are neither efficient nor
economical. (e.g. Using the 5 percent rule, if
the universe is 12 million, n 600,000 a very
large and costly result)
87Other Methods of Sample Size Determinationcont.
- Conventional sample size specification
- Conventional approach follows some convention
or number believed somehow to be the right sample
size (e.g. 1,000 1,200 used for national
opinion polls w/ 3 error) - Using conventional sample size can result in a
sample that may be too large or too small. - Conventional sample sizes ignore the special
circumstances of the survey at hand.
88Other Methods of Sample Size Determinationcont.
- Statistical analysis requirements of sample size
specification - Sometimes the researchers desire to use
particular statistical technique influences
sample size. As cross comparisons go up cell
sizes go up and n goes up. - Cost basis of sample size specification
- Using the all you can afford method, instead of
the value of the information to be gained from
the survey being the primary consideration in
sample size determination, the sample size is
based on budget factors.
89Special Sample Size Determination
Situations Sample Size Using Nonprobability
Sampling
- When using nonprobability sampling, sample size
is unrelated to accuracy, so cost-benefit
considerations must be used
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91Theoretical Framework and Hypothesis Development
-
- Theoretical framework is a conceptual model
which shows the relationships between factors
affecting a phenomenon. - It is based on previous research that are tested.
92When developing theoretical frameworks
- Determine the relevant variables and define them
- State the relationships between 2 or more
variables and their directions - Determine the direction of relationships among
variables - Explain why this direction of the relationship is
expected
93Types of Variables
- Dependent variable
- The main variable that is the main interest of
the research - The aim is to explain the change in this variable
- Brand preference, brand loyalty, customer
satisfaction, evaluation of advertising campaign - Export performance, Perceived image of Brand X
- Independent variable
- The variable which affects the dependent
variable, in other words - Which causes the change in the dependent variable
- Store preference-------- planned shopping
behaviour - Adoption of internet banking------- age
- Factors affecting supermarket preference --------
the importance given to price
94Types of Variables
- Mediating variable
- The variable which is creates the necessary
condition to have the relationship between the
dependent and the independent variable - Emotional attachment ------ consumer-company
identification---corporate image - Age------- shopping in supermarkets -------
frozen food - Intervening variable
- The variable which emerge during the period in
which the affect of independent variables impact
on the dependent variable is assessed
95Hypothesis
- The testable statements which assert the
relationships that are pre-determined on the
basis of theoretical framework -
- If-then statements
- Directional or non-directional statements
-
- NULL and ALTERNATIVE HYPOTHESIS
- H0 It states the relationship that we do not
want to find. -
- We expect to reject this hypothesis
- Therefore, we should formulate the statement in
the NULL hypothesis as something we do not prefer
to happen.
96Examples
- The firms will launch the product to a certain
market if the market share is more than 10 -
- H0 ? ? 0.10
- Ha ? ?0.10
-
- The new formula of the X product should bring a
better market share than the existing version of
the product X -
- H0 ?? 0.10 Ha ??0.10
- H0 ? ? ? Ha ? ? ?
97Alternative Hypotheses Examples
- Ha There is a relationship between internet
banking and prior experience about technological
products. -
- Ha There is a relationship between usage of
marketing research in international markets and
firm size. -
- Ha Status of foreign partnership in capital
affect technology usage in logistics activities. -
- Ha When brand preference is assessed, there is a
difference between less loyal and more loyal
consumers groups on brand reputation. -
- Ha Age and gender affect purchase intention.
98Hypothesis test types
- Two major aims
- Understanding differences
- Understanding relationships
-
- Univariate tests
- There is only one measurement for an item in a
sample - Variables are tested individually
-
- Multivariate tests
- There are 2 or more measurement for
observationVariables are tested simultaneously