Welcome Back

1
Welcome Back

• Learning Objectives
• Identify variables in research
• Describe Relationships btwn
• Explain why samples used to describe population
• Explain random sampling and representative
  samples
• Distinguish btwn Descriptive Inferential Stats
• Distinguish btwn experimental correlational
  study
• Identify distinguish scales of measurement

2
Research Process

• Interest in something
• Playing video games leads to violence
• Goal Discover LAWS OF NATURE
• Somethings are called Variables
• Variables
• Independent variables- the thing that
  influences the behavior
• Dependent variables- the outcome or result of the
  independent variable

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Examples of Variables

• Independent
• Vegetables
• Vitamins
• Drugs
• Smiling
• Examples?

• Dependent
• Cancer
• Immune System
• Alzheimers
• Helping or Altruism
• Examples?

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Relationship between Variables

• Relationship occurs when a chg in one var. is
  accompanied by a consistent chg. in another var.
• Strength Degree of chg in X is associated with
  chg in Y
• Types of relationships
• Increase, increase
• Increase, decrease
• Decrease, decrease
• Zero

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Populations Samples

• Population-all members of group
• Parameters-numbers that describe

• Sample-subset of pop designed to be
  representative
• Statistic-numbers that describe

Every student at BC
Students in a History class at BC
6

• http//www.ruf.rice.edu/lane/stat_sim/sampling_di
  st/
• Why?
• Cheaper
• Practical
• Representative

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What is done to samples?

• Describe
• Use descriptive statistics to organize
  summarize characteristics of data
• Example The average test score was 87
• Infer
• Use inferential statistics to decide whether
  sample data represents a particular relationship
  in population
• Example Reading the textbook significantly
  increased test scores.

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Characteristics of a Study

• Question about characteristic of sample or pop is
  asked
• Design study to answer question
• Who -How many -When -What
• Conduct study
• Correlational
• Experimental

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Correlational Study

• Goal To determine if relationship btwn two or
  more var is present
• No variables are manipulated or made to occur,
  they are simply measured
• As such? cannot infer causality
• Cant say X causes Y
• Only X and Y are related

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Example

• Researchers Question
• -Is there a relationship btwn ice cream sales
  and crime rate?
• Design of study measure sales crime rates
• Yes, a positive, strong relationship is present
• Doesnt mean ice cream causes crime

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Experimental Study

• Goal To determine if relationship (causality)
  exists btwn variables
• Variable (indep) are manipulated or changed to
  see chg in beh (dep var)
• Can infer causality
• X causes chg in Y
• Caution causal statement based on probability
• Never says PROVES
• Other variables could be responsible for change
  in dependent variable

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Example

• Researchers Question
• -Does ice cream cause or have an effect on
  criminal behavior
• Design of study Ps in diff conditions of ice
  cream (levels of indep var) and measure criminal
  beh (dep var)
• Yes, a probable causal relationship is present
• Ps that ate 1 or 2 scoops of ice cream committed
  more crimes
• PROBABILITY

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Type of Data or Characteristics of Scores

• Type of data or dependent var youre interested
  in will determine what statistic you can use
• Numbers you record have diff mathematical
  characteristics
• Characteristics of numbers
• Levels of measurement
• Continuous or discrete

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Scales of Measurement

• Nominal Scale scores used for identification or
  naming. Ex categories
• Ordinal Scale scores indicate rank or ordering.
  Ex relative amount
• Interval Scale scores indicate actual amount.
  Ex numbers
• 0 doesnt necessarily mean non
• Ratio Scale scores indicate actual amount Ex
  numbers (0 actually means none)

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Continuous or Discrete

• Continuous allows fractional amounts (continues
  btwn whole numbers)
• Usually Scale (ratio interval)
• Test score 97.6
• IQ score 145.9
• Discrete measures only whole numbers
• Usually Nominal or Ordinal
• Male or Female
• Eye color
• Can be Scale
• Ice cream or no ice cream
• No. of crimes 3

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Lets Graph
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Questions?

• Lets get Active with a CLE
• Homework Finish Ch.1 2 study guid
• Review notes text
• Finish Ch. 1 2 of study guide
• Preview Ch. 3
• Bring
• Questions, book, calculator, pencils
• Be ready for quiz