Enter your data for Item Analysis

Stat > Multivariate > Item Analysis

Specify the data for your analysis and indicate whether to standardize the variables.

In This Topic

Enter your data
Standardize variables

Enter your data

In Variables, enter the columns of data that you want to analyze. You must have two or more columns of numeric data. Each column contains responses to a survey or to a test item. You must have at least two non-missing values in each column. If a missing value exists in any column, Minitab ignores the entire row.

In this worksheet, each column contains the customer responses, on a 5-point scale, to a different question on a customer satisfaction survey. Each row represents the responses of an individual customer.

C1	C2	C3
Question 1	Question 2	Question 3
5	2	3
2	2	4
3	5	2
4	4	4
1	2	1
4	3	4

Standardize variables

Select Standardize variables to have Minitab weight all the items in the test or survey equally. Minitab converts the items to a common scale and uses the standardized values to calculate Cronbach's alpha and omitted-variable correlations. The standardized values are used only to calculate statistics and are not stored in the worksheet.

Standardizing is good practice in most cases, and is particularly important when the items use different scales. Suppose item A is on a scale from 1 − 3, and item B is on a scale of 1 − 20. If the items are not standardized, Minitab weights the items by their variability and places more weight on item B than on item A due to the larger values of its scale. Because this is probably not the desired result, the items should be standardized to avoid this unequal weighting.