Success/Failure Data

Success/failure data is also referred to as discrete or attribute data. It involves recording data from a test for a unit when there are only two possible outcomes: success or failure. An example of this is a missile that gets fired once and it either succeeds or fails. The data types available for success/failure data entry are:

Sequential
Sequential with Mode
Grouped per Configuration

Sequential Data

For Sequential data, an item is tested with only two possible outcomes: success or failure. This could be a one-shot item such as a missile or an entire system that either succeeds or fails. The item is then inspected after each trial and redesigned/repaired before the next trial. Figure 3.9 shows an example of this data type.

Figure 3.9: Sequential data

Sequential with Mode Data

Often after failure analysis you know the reason for failure of a particular trial. If this is the case, the reason for each failure can also be used in the analysis. This data entry is identical to the Sequential data with the exception that a failure code, mode or ID is added after each failure. Figure 3.10 shows an example of this type of data.

Figure 3.10: Sequential with Mode data

Grouped per Configuration Data

This data type is used when multiple items, instead of a single item, are tested and the number of units that fail are recorded for each configuration. The row numbers that appear on the left side of the Data Entry Spreadsheet, shown in Figure 3.11, represent the unique configuration. For example, row 1 indicates configuration 1 in which 10 missiles were fired and 5 failed, row 2 indicates configuration 2 in which 8 missiles were fired and 3 failed, etc. The data can be cumulative or non-cumulative.

Figure 3.11: Grouped per Configuration data

Models for Success/Failure Data

The following models can be used to analyze Success/Failure data. Models and examples using the different data types are discussed in later chapters of this on-line reference.

Duane (Note: The Duane model is not available for Sequential Success/Failure Data with Mode.)
Crow-AMSAA (N.H.P.P.) (Note: The Crow-AMSAA (N.H.P.P) model is not available for Sequential Success/Failure Data with Mode.)
Lloyd Lipow
Gompertz
Modified Gompertz
Logistic