Worksheet Structure (Uncensored/Right-Censored Data)
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To perform reliability studies, enter a column showing the failure times of each sample. For systems with more than one cause of failure, you must also enter a column defining the failure mode. See Multiple Failure Modes (Right Censored Data).

Worksheet structure:

Singly censored data

Multiply censored data

 

Months

Censor

50

F

50

F

53

F

53

F

60

F

65

F

70

C

70

C

.

.

.

.

.

.

and so on

and so on

Months

Censor

50

F

53

F

60

C

65

C

70

F

70

F

50

F

53

F

.

.

.

.

.

.

and so on

and so on

The Censor column contains the corresponding censoring indicators: F designates an actual failure; C designates a unit that was removed from the test before failure.

The Censor column is optional for singly censored data, but required for multiply censored data.

Note

For observations with corresponding columns of frequency, see Using frequency columns.

Singly censored data

You can define the censoring in one of the following ways:

·    Censoring columns - Enter two columns for each sample, one column of failure times and a corresponding column of censoring indicators. The columns for each sample must be the same length, although pairs of columns from different samples can have different lengths.

Censoring indicators can be numbers or text. If you do not enter a censoring value in the Censor subdialog box, Minitab assumes the lower of the two values indicates censoring, while the higher one indicates an exact failure.

·    Time Censoring - Enter a column of failure times and the time at which to begin censoring.

Time censoring means that you run the study for a specified period of time. All units still running at the end time are time censored. This is known as Type I censoring on the right. In the example above, units are time censored at 70 months.

·    Failure Censoring - Enter a column of failure times and the number of failures at which to begin censoring.

Failure censoring means that you run the study until you observe a specified number of failures. This is known as Type II censoring on the right. You specify the number of failures at which to begin censoring. In the example above, units are failure censored at 70.

Multiply censored data

You must define the censoring using censoring columns.