LECTURE 4 ATTITUDE SCALING

THURSTONE SCALING Post WWI work on interests and attitudes during 1920s- both industrial and psychological research interests Thurstone proposed model based on jnd Assumed interval scale possible for respondents to respond to different stimuli Developed procedure to generate about 20 statements that a respondent would agree or disagree with, sum the items based on their interval scale value (positive or negative items, scored appropriately)

THURSTONE SCALING Example: Attitude toward Abortion 10 statements positive toward abortion 10 statements negative toward abortion Respondent agreeing with positive statement receives 1 point for each Respondent disagreeing with negative statement receives 1 point each Possible range 0 - 20

THURSTONE SCALING A. Select single concept, idea, or construct for scaling eg. War, marriage, abortion, mathematics B. Collect 100-200 statements about the concept: non-factual, opinion-oriented C. Select about 80-100 for analysis. eg: I like arithmetic most of the time. Abortions should never be performed under any circumstances. War is usually a good thing, everything considered.

THURSTONE SCALING D. Place statements along 11 point continuum from (-) 1= most negative statement to (+) 11= most positive statement, with 6= neutral or nonjudgmental statement. - use 50-200 subjects to do placement - evaluate distribution of each statement:

THURSTONE SCALING Median of item as scale value: for example, statement: Abortions should never be performed. 1 2 3 4 5 6 ... n: 150 50 0 0 0 0  %ile 50 score 1.17

THURSTONE SCALING for example, statement: Abortions should be performed only to save the life of the mother. 1 2 3 4 5 6... n: 10 40 90 40 20 0  %ile 50 score 3.05

THURSTONE SCALING Variability: Eliminate items with ranges > 6 or 7 Examine conditional distributions of adjacent or close items: Give items to 200-300 respondents to endorse each statement (+) agree or (-) disagree Examine joint endorsements of one item (a) with another (b), using an index such as Ia,b = nab / nb

THURSTONE SCALING The distribution of the aIb ‘s should decrease around item a on either side of its scale value; that is, items with similar scale values should have a high similarity index, while items further away on the scale should have scale values that drop away with distance. Throw out items with poor characteristics.

ItemScale Value = 5.5 I n d e x of S i m l a r t y 1 2 3 4 5 6 7 8  9 10 11

LIKERT SCALING Renses Likert (1930’s) researched the Thurstone procedure - Placement, scale valuation procedure is cumbersome - Likert replaced it with: 1=strongly disagree 2=disagree 3=uncertain 4=agree 5=strongly agree

LIKERT SCALING Give items to sample of target population Use classical techniques to select items: item mean, SD, interitem correlation Theoretical justification: items are samples of the normal distribution shifted along the 1-5 continuum so that the mean is at the scale value

Item with scale value 1.5 1 2 3 4 5

Item with scale value 3.0 1 2 3 4 5

RATING SCALES Derivatives of Likert scaling Alternative adjective set (1..5) Requires distributional validation Even # points is problematic Less well investigated

RATING SCALE VALUES Number of scale values: 1 to 5 based on Likert 7, 9, or 11 can be useful for finer discriminations Dependent on population, concept being assessed

SEMANTIC DIFFERENTIAL Osgood, Suci, & Tannenbaum Bipolar adjective pairs Represent: Strength: strong-weak, heavy-light Value: good-bad, useful-useless Activity: fast-slow, hot-cold Two factors usually found: Evaluation and Activity/Strength

SOME ADDITIONAL IDEAS NON-NORMAL DISTRIBUTIONS: POISSON AND COUNT DATA FREQUENCY SCORE

SOME ADDITIONAL IDEAS NON-NORMAL DISTRIBUTIONS: POISSON AND COUNT DATA

DISTRIBUTIONAL ISSUES CENSORED: PART OF THE NORMAL (eg. LIKERT ITEMS)- SUMMING SHOULD CREATE NORMAL INDIVIDUAL ITEMS CAN BE ANALYZED AS CENSORED NORMAL SCORES OF INTEREST IN RELIABILITY AND VALIDITY STUDIES