Social Science Reasoning Using Statistics

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Social Science Reasoning Using Statistics

• Psychology 138
• Spring 2007

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Producing Data
To understand data, we need to know about
the context from which the numbers were derived.
Money in proposed budget to set up
prescription-drug registries
5.8
40
High school seniors reported using OxyContin
during the previous year
9.8 million
rise since 2002
Statistics in the news
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Producing Data

• Scientific method
• Research methods
• Observation methods
• Experimental methods
• Quasi-experimental
• Variables
• Types
• Operational definitions
• Sampling
• Samples and populations
• Statistics and parameters
• Techniques

• Basic Probability
• Measurements
• Continuous and discrete
• Scales of measurement
• Instrument
• Validity
• Internal and external
• Confounds
• Bias
• Reliability
• Experimental control

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In the news

• The researchers used a questionnaire to interview
  a random sample of 351 people ages 20 to 80 in
  the Vancouver, British Columbia, area, asking
  about their dog ownership and level of physical
  activity.
• Dog owners walked almost twice as many minutes
  per week as people who did not own dogs, and the
  dog owners spent more time in all forms of mild
  and moderate physical activity.
• Neither the sex of the owner nor the size of the
  dog made a difference men and women who owned
  dogs participated in increased amounts of
  moderate exercise compared with those who had no
  dog. But no statistically significant difference
  between the two groups was evident in the amount
  of strenuous exercise performed.
• The authors concede that the study, published in
  the February issue of The American Journal of
  Preventive Medicine, does not determine whether
  owning a dog itself makes people exercise more.
• Shane Brown, the study's lead author and a
  graduate student at the Behavioral Medicine
  Laboratory of the University of Victoria, called
  this "the million-dollar question."
• When the researchers subtracted the time spent
  walking the dog from total physical activity, dog
  owners actually walked less than their
  counterparts without dogs.
• This, the researchers say, may suggest that the
  dog makes the difference. When dog owners choose
  to engage in moderate physical exercise, the
  reason may be that a four-legged member of the
  household is insisting on a walk. Now.
• American Journal of Preventive Medicine (2006,
  302)

Regimens Pounding the Pavement, Stopping at Fire
Hydrants
People who own dogs appear to get more exercise
than those who do not
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In the news

• The research process
• Ask the research question
• Identify variables and formulate the hypothesis
• Define your population
• Select a research methodology
• Collect your data from a sample
• Analyze your data
• Draw conclusions based on your data
• Repeat

Regimens Pounding the Pavement, Stopping at Fire
Hydrants
People who own dogs appear to get more exercise
than those who do not
6
In the news

• The research process
• Ask the research question
• Identify variables and formulate the hypothesis
• Define your population
• Select a research methodology
• Collect your data from a sample
• Analyze your data
• Draw conclusions based on your data
• Repeat

Regimens Pounding the Pavement, Stopping at Fire
Hydrants
People who own dogs appear to get more exercise
than those who do not
7
In the news

• The research process
• Ask the research question
• Identify variables and formulate the hypothesis
• Define your population
• Select a research methodology
• Collect your data from a sample
• Analyze your data
• Draw conclusions based on your data
• Repeat

Regimens Pounding the Pavement, Stopping at Fire
Hydrants
People who own dogs appear to get more exercise
than those who do not
8
In the news

• The research process
• Ask the research question
• Identify variables and formulate the hypothesis
• Define your population
• Select a research methodology
• Collect your data from a sample
• Analyze your data
• Draw conclusions based on your data
• Repeat

• Variables
• Operational level
• Conceptual level

Regimens Pounding the Pavement, Stopping at Fire
Hydrants

• Variables
• Independent (explanatory) variables
• Dependent (response) variable
• Control variables
• Random variables
• Confound variables

The researchers , asking about their dog
ownership and level of physical activity.
Methods . Questionnaires were mailed out in 2004
to collect information about demographics, dog
ownership, leisure-time walking, physical
activity levels, and theory of planned behavior
(TPB) constructs.
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In the news

• The research process
• Ask the research question
• Identify variables and formulate the hypothesis
• Define your population
• Select a research methodology
• Collect your data from a sample
• Analyze your data
• Draw conclusions based on your data
• Repeat

Regimens Pounding the Pavement, Stopping at Fire
Hydrants
Instrument used?

• Scales of measurement
• Nominal
• Ordinal
• Interval
• Ratio

The researchers , asking about their dog
ownership and level of physical activity.
- men women, own dog or not
- mild, strenuous
Methods . Questionnaires were mailed out in 2004
to collect information about demographics, dog
ownership, leisure-time walking, physical
activity levels, and theory of planned behavior
(TPB) constructs.
- time spent exercising
10
In the news

• The research process
• Ask the research question
• Identify variables and formulate the hypothesis
• Define your population
• Select a research methodology
• Collect your data from a sample
• Analyze your data
• Draw conclusions based on your data
• Repeat

Is the sample representative? Is there any bias
in the sample?
Regimens Pounding the Pavement, Stopping at Fire
Hydrants
The researchers used a questionnaire to interview
a random sample of 351 people ages 20 to 80 in
the Vancouver, British Columbia, area,
Was it simple random sampling? Stratified random
sampling? Etc.?
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In the news

• The research process
• Ask the research question
• Identify variables and formulate the hypothesis
• Define your population
• Select a research methodology
• Collect your data from a sample
• Analyze your data
• Draw conclusions based on your data
• Repeat

Regimens Pounding the Pavement, Stopping at Fire
Hydrants
Causal Claims??
The researchers used a questionnaire to interview
a random sample of 351 people ages 20 to 80 in
the Vancouver, British Columbia, area,

• Which Research Method??
• Observational study
• Experimental methodology
• Quasi-experimental methodology

The authors concede that the study does not
determine whether owning a dog itself makes
people exercise more.
This may suggest that .. when dog owners choose
to engage in moderate physical exercise, the
reason may be that the dog is insisting on a
walk.
12
In the news

• The research process
• Ask the research question
• Identify variables and formulate the hypothesis
• Define your population
• Select a research methodology
• Collect your data from a sample
• Analyze your data
• Draw conclusions based on your data
• Repeat

Regimens Pounding the Pavement, Stopping at Fire
Hydrants
Possible confounds? Threats to internal validity?
If follow-up as an experiment were designed, what
would you do?
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Producing Data

• Scientific method
• Research methods
• Observation methods
• Experimental methods
• Quasi-experimental
• Variables
• Types
• Operational definitions
• Sampling
• Samples and populations
• Statistics and parameters
• Techniques

• Basic Probability
• Measurements
• Continuous and discrete
• Scales of measurement
• Instrument
• Validity
• Internal and external
• Confounds
• Bias
• Reliability
• Experimental control

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Basic Probability
Random events are unpredictable in the short
term
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Flipping a coin example
Random events are unpredictable in the short
term
But predictable in the long run.
Number of heads
2
1
1
0
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Flipping a coin example
Random events are unpredictable in the short
term
But predictable in the long run.
Number of heads
2
1
1
0
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Flipping a coin example
What about a longer run?
Number of heads
Eight total outcomes
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Flipping a coin example
Number of heads
3
2
2
1
2
1
1
0
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Flipping a coin example
Each flip of the coin is independent of previous
flips
So this is a different question than Asking
whats the probability of flipping 4 heads in a
row.
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Producing Data

• Scientific method
• Research methods
• Observation methods
• Experimental methods
• Quasi-experimental
• Variables
• Types
• Operational definitions
• Sampling
• Samples and populations
• Statistics and parameters
• Techniques

• Basic Probability
• Measurements
• Continuous and discrete
• Scales of measurement
• Instrument
• Validity
• Internal and external
• Confounds
• Bias
• Reliability
• Experimental control