reliability and validity of researcher-made surveys
TRANSCRIPT
Reliability and Validity of Researcher-Made Surveys
Reliability
Reliability
“Authors should provide
reliability coefficients of
the scores for the data
they analyze even when
the focus of their
research is not
psychometric.”
Reliability
“Authors should provide
reliability coefficients of
the scores for the data
they analyze even when
the focus of their
research is not
psychometric.”
Reliability is the amount
of random fluctuation in
individual scores.
Reliability
“Authors should provide
reliability coefficients of
the scores for the data
they analyze even when
the focus of their
research is not
psychometric.”
Reliability is the amount
of random fluctuation in
individual scores.
“In practice, score
reliability is a matter of
degree, because all
scores include some
random fluctuation.”
Reliability
“It is the reliability of the data in hand in a given study that will drive study results, not the reliability of the scores described in the test manual.”
Reliability is the amount
of random fluctuation in
individual scores.
“In practice, score
reliability is a matter of
degree, because all
scores include some
random fluctuation.”
Reliability
“It is the reliability of the data in hand in a given study that will drive study results, not the reliability of the scores described in the test manual.”
“Poor score reliability
may compromise …
score ‘validity’.”
“In practice, score
reliability is a matter of
degree, because all
scores include some
random fluctuation.”
Reliability
“It is the reliability of the data in hand in a given study that will drive study results, not the reliability of the scores described in the test manual.”
“Poor score reliability
may compromise …
score ‘validity’.”
“Poor score reliability
may compromise the
ability of a study to yield
noteworthy effects”
Reliability
“Poor score reliability
may compromise …
score ‘validity’.”
“Poor score reliability
may compromise the
ability of a study to yield
noteworthy effects”
Reliability
“Scores can’t both measure nothing and measure something.”
“Poor score reliability
may compromise …
score ‘validity’.”
“Poor score reliability
may compromise the
ability of a study to yield
noteworthy effects”
Reliability
“Scores can’t both measure nothing and measure something.”
“Perfectly unreliable scores are perfectly random and cannot yield… significant results.”
“Poor score reliability
may compromise …
score ‘validity’.”
“Poor score reliability
may compromise the
ability of a study to yield
noteworthy effects”
Reporting Reliability
“Scores can’t both measure nothing and measure something.”
“Perfectly unreliable scores are perfectly random and cannot yield… significant results.”
“Poor score reliability
may compromise …
score ‘validity’.”
“Poor score reliability
may compromise the
ability of a study to yield
noteworthy effects”
Reporting Reliability
Reporting Reliability
“Reporting reliability coefficients for one’s own data is the exception rather than the norm...Too few reliability estimates for analyzed data are provided in both journals…and doctoral dissertations.”
Reporting Reliability
“Reporting reliability coefficients for Reporting reliability coefficients for one’s own data is the exception one’s own data is the exception rather than the norm...rather than the norm...Too few Too few reliability estimatesreliability estimates for analyzed for analyzed data data are provided in both journals… both journals…and and doctoral dissertations.”
Reporting Reliability
“The most commonly used (reliability) estimate is Cronbach’s (1951) coefficient alpha ().”
“The most commonly used (reliability) estimate is Cronbach’s (1951) coefficient alpha ().”
number of items (sum of item variances)
number of items-1 test variance
Reporting Reliability
1-
“The most commonly used (reliability) estimate is Cronbach’s (1951) coefficient alpha ().”
“Item score covariance plays an important role in both the numerator and the
denominator of the estimate.”
Reporting Reliability
“The most commonly used (reliability) estimate is Cronbach’s (1951) coefficient alpha ().”
“The intercorrelations of the items are the essential source of this
kind of reliability.”
Reporting Reliability
Validity of Researcher-Made Surveys
Evidence of Validity
Evidence of Validity
• Patterns of Association
Evidence of Validity
• Patterns of Association
• Comparing Results from Different Versions of the Same Question
Evidence of Validity
• Patterns of Association
• Comparing Results from Different Versions of the Same Question
• Comparing Responses to Data from Other Sources
Evidence of Validity
• Patterns of Association
• Comparing Results from Different Versions of the Same Question
• Comparing Responses to Data from Other Sources
• Asking the Same Question Twice and Comparing Results
• Patterns of Association
• Comparing Results from Different Versions of the Same Question
• Comparing Responses to Data from Other Sources
• Asking the Same Question Twice and Comparing Results
Evidence of Validity
Reliability
Reliability
• Patterns of Association
Evidence of Validity
• Patterns of Association• Scores from different measures believed to measure
similar things should correlate. Scores from different measures believed not to measure similar things should not correlate.
• Responses to items believed to represent the same dimensions or factors should correlate.
Evidence of Validity
• Comparing Responses to Data from Other Sources
Evidence of Validity
• Comparing Responses to Data from Other Sources
• Compare to records. Compare to physical testing. Compare to population estimates.
Evidence of Validity
Face Validity of Survey Questions
Face Validity of Survey Questions
• Have a reason for every question you ask.
• Keep questions simple.
• Keep questions precise.
• Avoid leading questions.
• Foresee social desirability.
• Response options should be mutually exclusive and exhaustive.
• Provide temporal frame of reference.
• Use Likert format correctly.
Pilot Testing
Pilot Testing
• Sample size >15
• Discuss questions with respondents to find confusion or ambiguity.
• Pretest sample should resemble study sample.
• Examine variance among respondents.
• Refine answer options.
• Time how long it takes.
Group Assignment
Produce a Valid and Reliable Attitude or Psychological Scale in 90 Minutes
Produce a Valid and Reliable Attitude or Psychological Scale in 90 Minutes
Write a 7 to 10 item scale. 30 minutes
Pilot test your items. 15 minutes Use another group. If necessary, revise your scale based on your pilot testing.
Administer the revised scale to 10 minutes at least 6 people. Collect data.
Enter data on SPSS. 20 minutes Compute coefficient alpha. Revise your scale based on reliability data.
Report. 15 minutes
Entering Survey Data on SPSSItem1 Item2 Item3
Survey1 4 1 5
Survey2 5 1 4
Survey3 4 2 3
Item 1 “I like salt.”
Strongly Disagree Disagree Neutral Agree Strongly Agree
1 2 3 4 5
Analyzing for Reliability in SPSS1. Enter survey data.2. Choose menu options:Analyze
ScaleReliability Analysis
3. Choose and move variables to Items box.4. Click Statistics…Click on: Item
ScaleScale if Item Deleted
5. Read output. Identify items which have an “Alpha if Item Deleted” larger than the scale’s Alpha. Remove those items.
6. Re-run analysis with remaining items until satisfied.