Introduction

Scales

Likert Scales

Bogardus
Social
Distance
Scales

Guttman
Scales

Indices

Additional Considerations

Typologies

Measurement
Error

Aids

Testing responses to items

After the data are collected, we need to conduct an item analysis to see the extent to which responses to each item are related to responses to the other items. If each is a valid indicator of socio-economic status, each item will show at least a moderate relationship with the other items. If any item was not related to the other items, this would suggest that the item did not measure the same thing as the rest of the items. On the other hand, a very high relationship between any two items indicates that one item would do as well as the other and that both are not needed. In that case, we can delete one of the two items. A moderate relationship - not too high or not too low - suggests that the items are tapping a common dimension and that each will contribute independently to the total index score.

As a beginning researcher, you may be confused by the vague descriptions of "too high," "too low" or "moderate." After you read Chapter 19, particularly our description of correlation analysis, you will have a better idea of the relative degrees of association between two variables. Right now, we want you to get the idea of testing items to see if they form an index.

The results of our item analysis are shown in Tables 7.5, 7.6, and 7.7. Before examining the results in the tables, we need to explain how they are constructed. (Chapter 18 provides further details on constructing tables). Table 7.5 shows the relationship between schooling and occupation; Table 7.6 reports results for the association of schooling with house type; and Table 7.7 provides the relationship between house type and occupation. Each table has parts, called cells. Using Table 7.5, for example, the four cells represent the logical combinations of low and high levels on each of the two variables. The cell in the upper left shows the number (N) of men with both a low level of schooling and a low occupational level. The cell in the lower left indicates how many men had a low level of schooling but who were classified as having a high occupational level. In Table 7.5, 112 men were classified as having a low level of schooling and a low level of occupation.   The other 38 men with a low level of schooling were classified as having high-level occupations. The right set of cells show frequencies for men with a higher level of schooling, but who differed in terms of occupational levels.  

Table 7.5. Item analysis for schooling and occupation

In addition, each cell includes a percentage column. Table 7.5 shows that the 112 men in the low-low cell represented 75% of all men with a low level of schooling. Totals for cells are shown at the bottom and on the right side of each table. Going down the columns, the Ns add to the total number for the indicator shown on the top line. In Table 7.5, the total for all men with a low level of schooling was 150. Another 50 men had a high level of schooling. The corresponding percentages add to 100. The total column to the right shows the total for occupation, the other indicator in the relationship. Of the 200 men in the total sample, 130 were classified as having a low-level occupation and 70 were placed in the high-level. The other two tables are constructed and "read" in the same way.

Now, we turn to the results of the item analyses. Table 7.5 shows a clear relationship between levels of schooling and occupations. Seventy five percent (75%) of the men with a low level of schooling also were classified as having a low-level occupation. A mismatch on these two indicators occurred for 25 % of the men. Sixty five persons (65%) of the men with a high level of schooling also were classified as having a high level occupation. The mismatch in this case was 35%. Clearly, the two indicators are related. For a large majority of men, a low level of schooling was associated with a low level of occupation. Most men with a high level of schooling also had high occupational levels.

As shown in Table 7.6, schooling and house type were also associated, although not as strongly as for occupation and schooling. Sixty three percent (63%) of the men with a low level of schooling also lived in what were defined as low-level houses. For men with a high level of education, 60% lived in residences classified as high level.