Correlational Research

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Correlational Research

• Goal Describe the relationship between two
  variables in terms of
• Direction
• Strength
• Pearson Correlation Coefficient
• -1 ? 0 ? 1

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• Testing the significance of a correlation
• Is the correlation significantly different from
  zero?
• Null hypothesis The correlation between Social
  Support and Life Satisfaction is not
  significantly different from zero.
• Alternative hypothesis The correlation between
  Social Support and Life Satisfaction is
  significantly different from zero

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• Conclusion A significant correlation between
  Social Support and Life Satisfaction was
  observed, r (3) .884, p lt .05.

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The Squared Correlation

• r r2
• 0 0
• .1 .01
• .2 .04
• .3 .09
• .4 .16
• .5 .25
• .6 .36
• .7 .49
• .8 .64
• .9 .81
• 1.0 1.0

The squared correlation provides the proportion
of overlap between the two variables.
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Correlation and Cause and Effect

• Requirements for a conclusion regarding cause and
  effect
• Time-Order relationship
• Cause ? Effect
• Cant know which variable occurred first.
• No other variable is responsible for the
  relationship.
• The Third Variable Problem

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Survey Methods

• Types of questions
• Open-ended
• Close-ended
• Partially open-ended (Other is added as an
  alternative response)
• Rating Scale
• Likert rating scale. To what degree does the
  respondent agree with a statement.

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Likert-type Item

• How much do you agree with the following
  statement?
• I plan to dedicate the rest of my life to
  learning more about statistics.
• 1-------------2------------3------------4--
  ----------5
• Strongly Disagree
  Neutral Agree
  Strongly
• Disagree
  
  Agree

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Reversed Likert-type Item

• How much do you agree with the following
  statement?
• My hatred for statistics extends to the very
  core of my being.
• 1-------------2------------3------------4--
  ----------5
• Strongly Disagree
  Neutral Agree
  Strongly
• Disagree
  
  Agree

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Types of items to avoid

• Loaded question
• Includes non-neutral or emotionally laden terms
• Ex. What is your opinion of the hideous new
  statue?
• Leading question
• Attempts to influence the response
• Example. Shouldnt first-year students be allowed
  to bring a car to campus?
• Double barreled question
• Asks for more than one piece of information in a
  single item.

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Sampling Techniques

• Probability Sampling
• Random selection
• Stratified random sample
• Cluster sampling
• Non-Probability sampling
• Convenience sampling
• Quota sampling

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