Quality and Reliability Methods - SAS

264 Recurrence Analysis Chapter 15
Examples
Cost is a column that must contain one of the following values:
• a 1, indicating that an event has occurred (a unit failed or was repaired, replaced, or adjusted). When
indicators (1s) are specified, the MCF is the mean cumulative count of events per unit as a function of
age.
• a cost for the event (the cost of the repair, replacement, or adjustment). When costs are specified, the
MCF is a mean cumulative cost per unit as a function of age.
• a zero, indicating that the unit went out-of-service, or is no longer being studied. All units (each System
ID) must have one row with a zero for this column, with the Y, Age, Event Timestamp column
containing the final observed age. If each unit does not have exactly one last observed age in the table
(where the Cost column cell is zero), then an error message appears.
Note: Cost indicators for Recurrence Analysis are the reverse of censor indicators seen in Life
Distribution or Survival Analysis. For the cost variable, the value of 1 indicates an event, such as repair; the
value of 0 indicates that the unit is no longer in service. For the censor variable, the value of 1 indicates
censored values, and the value of 0 indicates the event or failure of the unit (non-censored value).
Grouping produces separate MCF estimates for the different groups that are identified by this column.
Cause specifies multiple failure modes.
Timestamp at Start specifies the column with the origin timestamp. If you have starting times as event
records, select the First Event is Start Timestamp option instead. JMP calculates age by subtracting the
values in this column.
Timestamp at End specifies the column with the end-of-service timestamp. If end times are given for all
units, specify that column here. If end times are not given for all units, specify the Default End Timestamp
option instead. But if you have a record in which Cost is equal to zero, JMP uses that record as the end
timestamp and you do not need to specify this role.
Age Scaling specifies the time units for modeling. For example, if your timestamps are coded in seconds,
you can change them to hours.
Examples
Valve Seat Repairs Example
A typical unit might be a system, such as a component of an engine or appliance. For example, consider the
sample data table Engine Valve Seat.jmp, which records valve seat replacements in locomotive engines. See
Meeker and Escobar (1998, p. 395) and Nelson (2003). A partial listing of this data is shown in Figure 15.2.
The EngineID column identifies a specific locomotive unit. Age is time in days from beginning of service to
replacement of the engine valve seat. Note that an engine can have multiple rows with its age at each
replacement and its cost, corresponding to multiple repairs. Here, Cost=0 indicates the last observed age of
a locomotive.