Russel-Research-Method-in-Anthropology

Scales and Scaling 331
interitem correlation and (2b) Cronbach’s alpha, and (3) taking the itemtotal
correlation.
1. Scoring the Responses
The first thing to do is make sure that all the items are properly scored.
Assume that we’re trying to find items for a scale that measures the strength
of support for training in research methods among anthropology students.
Here are two potential scale items:
Training in statistics should be required for all undergraduate students of anthropology.
1 2 3 4 5
Strongly Disagree Neutral Agree Strongly
disagree
agree
Anthropology undergraduates don’t need training in statistics.
1 2 3 4 5
Strongly Disagree Neutral Agree Strongly
disagree
agree
You can let the big and small numbers stand for any direction you want, but
you must be consistent. Suppose we let the bigger numbers (4 and 5) represent
support for training in statistics and let the smaller numbers (1 and 2) represent
lack of support for that concept. Those who circle ‘‘strongly agree’’ on
the first item get a 5 for that item. Those who circle ‘‘strongly agree’’ on the
second item get scored as 1.
2a. Taking the Interitem Correlation
Next, test to see which items contribute to measuring the construct you’re
trying to get at, and which don’t. This involves two calculations: the intercorrelation
of the items and the correlation of the item scores with the total scores
for each informant. Table 12.3 shows the scores for three people on three
items, where the items are scored from 1 to 5.
To find the interitem correlation, we would look at all pairs of columns.
There are three possible pairs of columns for a three-item matrix. These are
shown in table 12.4.
A simple measure of how much these pairs of numbers are alike or unalike
involves, first, adding up their actual differences, Σ d , and then dividing this by
the total possible differences, Max d .
In the first pair, the actual difference between 1 and 3 is 2; the difference