Data - Probit Analysis
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Enter the following columns in the worksheet:

·    two columns containing the response variable, set up in event/trial or response/frequency format

·    one column containing a stress variable (treated as a covariate in Minitab)

·    (optional) one column containing a factor

Response variable

The response data is binomial, so you have two possible outcomes, event (the unit fails) or non-event (the unit does not fail). You can enter the data in either event/trial or response/frequency format. Here is the same data arranged both ways:

Event/trial format

Response/frequency format

Temp

Events

Trials

 

Temp

Response

Frequency

 

80

2

10

 

80

1

2

 

120

4

10

 

80

0

8

 

140

7

10

 

120

1

4

 

160

9

10

 

120

0

6

 

The Events column contains the number of events (failures). The Trials column contains the number of observations. For example, when Temp = 140, there were seven events (failures) and three non-events (non-failures).

140

1

7

 

140

0

3

 

160

1

9

 

160

0

1

 

The Response column contains values which indicate whether the unit failed or not. The higher value corresponds to an event (the unit failed). The Frequency column indicates how many times that observation occurred. For example, when Temp = 160, there were nine events (the unit failed) and one non-event (the unit did not fail).

Factors

Text categories (factor levels) are processed in alphabetical order by default. If you wish, you can define your own order - see Ordering Text Categories.