Multiple item scales

Attitudes are composed of many elements. In the study of brands some of the elements measured were: quality, price, value, prestige, dependability etc. The graphic rating scales provide a measure of the respondent’s reaction to each element but are not good for summarizing all elements into one measure. To provide one such summary measurement, multi-item scales have been developed. Two of the best known are the Thurstone and Likert scales. Rather than ask individuals for self assessments, these techniques develop a series of statements related to the attitude. Individuals are asked to indicate agreement or disagreement with the statements and, on the basis of the responses, scores are determined that measure each individual’s attitude. Each of these two methods is discussed in more detail below.

Thurstone Scale: Thurstone developed his method of equal appearing intervals on the concept that, even though people could not assign quantitative measurements to their own attitudes, they could tell the difference between the attitude represented by two different statements and could identify that were approximately halfway between the two. The procedure is as follows:

1) Collect a large number of statements (perhaps as many as several hundred) related to the attitude in question.
2) Have a number of judges (perhaps 20 or more) sort the statements independently into 11 piles that vary from the most unfavorable statements in pile one, to neutral statements in pile 6, to the most favorable statements in pile 11.
3) Study the frequency distribution of ratings for each statement and eliminate those statements that different judges have given widely scattered ratings that are in a number of different piles.
4) Determine the scale value of each of the remaining statements – that is the number of the pile in which the median of the distribution falls.
5) Select one or two statements from each of the 11 piles for the final scale. Those statements with the narrowest range of ratings are preferred as the most reliable. List the selected statements in random order to form the final scale.

The following statements are taken in order, one from each of the 11 positions, from a scale to measure attitude toward television commercials:

1) All TV commercials should be prohibited by law.
2) Watching TV commercials is a complete waste of time.
3) Most TV commercials are pretty bad.
4) TV commercials are monotonous
5) TV commercials do not interfere too much with enjoying TV.
6) I have no feeling one way or the other about most TV commercials
7) I like TV commercials at times
8) Most TV commercials are fairly interesting
9) I like to buy products advertised on TV whenever possible.
10) Most TV commercials help people select the best products available
11) TV commercials are more fun to watch than the regular programs.

Respondents whose attitudes are to be scaled are given the list of statements and asked to indicate agreement or disagreement with each statement. Presumably each respondent will agree with only one statement or with a few statements that are from immediately adjacent scale positions. For example, a respondent might agree with statements the scale values of which were 8, 9, and 10. Such an agreement in the above list would be interpreted as representing a favorable attitude toward television commercials. Respondents’ scores are computed as the median of the item numbers with which they agree. If respondents agreed with statements 1, 4, 7 and 11, it would be interpreted to indicate they did not have organized attitudes on the topic. If the scale has been properly prepared, few respondents should show such a varied group of attitudes.