Asking Good Questions Chapter 7

Scales of Measurement Nominal Nominal Ordinal Ordinal Interval Interval Ratio Ratio

Nominal Level Data Identification Identification Examples: Examples: Mode Mode Source: packers.wikia.com

Ordinal Level Data Order Order Examples: Examples: Median Median Source: collegefootballpoll.com

Interval Level Data Can compare based on size of differences among and between members Can compare based on size of differences among and between members Examples: Examples: Mean Mean Source: en.wikipedia.org

Ratio Level Data Absolute zero and comparison of absolute magnitudes Absolute zero and comparison of absolute magnitudes Examples: Examples: Mean Mean Source:

Measuring Attitudes Self-reports Self-reports Itemized-Rating Scales Itemized-Rating Scales Likert-scales Likert-scales Semantic differential scales Semantic differential scales Graphic rating scales Graphic rating scales Comparative rating scales Comparative rating scales Constant sum scale Constant sum scale Halo effect Halo effect

Other Considerations Number of Items Number of Items Global measures Global measures Composite measures Composite measures Number of Scale Positions Number of Scale Positions Include “Don’t Know” or “N/A”?? Include “Don’t Know” or “N/A”??

Establishing Validity & Reliability Two types of errors Two types of errors Systematic error Systematic error Random error Random error Validity Validity “Extent to which differences in scores on an instrument measure true differences among individuals on the characteristic it intends to measure” “Extent to which differences in scores on an instrument measure true differences among individuals on the characteristic it intends to measure” Reliability Reliability