Psychometrics
arnold on Oct 05, 2008
Thurstone invented three different methods for developing a unidimensional scale. The three methods differed in how the scale values for items were constructed, but in all three cases, the resulting scale was rated the same way by respondents. The rest of this example will concentrate on his Method of Equal-Appearing Intervals.
Steps from SocialResearchMethods.net
1) The first step is the development of the focus for the scaling project.
2) You then gather a large set of candidate statements.
3) You then have your judges rate their agreement or disagreement of the statements on an 11 point scale.
4) Then you analyze the rating data. For each statement, you need to compute the Median and the Interquartile Range.
5) Next, you have to select the final statements for your scale. You should select statements that are at equal intervals across the range of medians. You now have a scale, a yardstick you can use for measuring attitudes.
6) You can give it to participants and ask them to agree or disagree with each statement. To get that person’s total scale score, you average the scale scores of all the items that person agreed with.
For example:
It should be noted that Barclay and Weaver (1962) compared Likert with Thurstone scale and found that Likert exhibited a higher degree of reliability. Additionally, they agreed that Likert was easier to carry out.
Most information was taken from SocialResearchMethods.net. Please visit their site for an in-depth review of this concept.
