Parametric RDA Folio Quick Calculation Pad (QCP)

The Quick Calculation Pad (QCP) provides a quick and accurate way of calculating a variety of useful metrics related to recurrent event data analysis. To access the tool, choose Recurrent Event Data > Analysis > Quick Calculation Pad or click the icon on the Main page of the control panel.

How to Use the QCP

If you select Both One-Sided, the QCP will calculate both the lower one-sided bound and the upper one-sided bound.

Under the log display, you can also click Feed to "advance the tape" or Clear to delete all data from the current log. If you click inside the log, you can copy some or all of the text to the clipboard.

QCP Calculations

Each type of calculation may require additional user inputs in order to solve for the metric of interest.

Failure Intensity

Calculates the average rate of occurrence of failures from time = 0 up to a specified end time. Enter the end time in the Time field. For example, a cumulative failure intensity of 0.15 from 0 to 100 hours means that, on average, 0.15 failures occurred every hour over the 100-hour period.

Calculates the rate of occurrence of failures over a small interval dt that begins at a specified time. Enter the time in the Time field. For example, an instantaneous failure intensity of 0.15 at 100 hours means that, over the next small interval dt that begins at 100 hours, the rate of occurrence of failures is 0.15 failures per hour.

MTBF (Mean Time Between Failures)

Calculates the average MTBF from time = 0 up to a specified end time. Enter the end time in the Time field. For example, a cumulative MTBF of 5 hours from 0 to 100 hours means that, on average, the time between failures was 5 hours over the 100-hour period.

Calculates the average MTBF over a small interval dt that begins at a specified time. Enter the time in the Time field. For example, an instantaneous MTBF of 5 hours at 100 hours means that, over the next small interval dt that begins at 100 hours, the average MTBF will be 5 hours.

Note: MTBF is used as a metric for the analysis of repairable components. On the other hand, the term mean time to failure (MTTF) is used as a metric for non-repairable systems, where components are discarded or replaced upon failure. To analyze non-repairable system data in Weibull++, use the Weibull++ standard folio.

Failures

Calculates the cumulative number of failures to be expected for a specified interval of time. Enter the start time of the interval in the Mission Start Time field and enter the duration of the interval in the Mission Additional Time field. For example, a system may be estimated to fail 10 times between 100 and 500 operating hours.

Calculates the cumulative number of failures to be expected for each system for a specified interval. The start time of the interval is equivalent to the time when the observation period for the system ended (indicated by an E in the folio data sheet). If you did not enter an end time for a system, then the start time of the interval is assumed to be equal to the last failure time for that system. Enter the duration of the interval in the Mission Additional Time field and then click Calculate to open the Results window, which shows the cumulative number of failures for each system, as well as the overall number of failures.

Probability

Calculates the probability of the system successfully completing a mission, given that it may or may not have successfully completed a previous mission. Enter the start time of the new mission in the Mission Start Time field and enter the duration of the new mission in the Mission Additional Time field.

For example, a system failed 3 times during its first three years of operation. The probability that the system will operate for an additional six months without failure, or the conditional reliability for one half of a year given that the system is three years old, may be 30%.

Calculates the probability that the system will fail a mission, given that it may or may not have successfully completed a previous mission. Enter the start time of the new mission in the Mission Start Time field and enter the duration of the new mission in the Mission Additional Time field.

For example, a system failed three times during its first three years of operation. The probability that the system will fail in the next six months, or the conditional probability of failure for one half of a year given that the system is three years old, may be 70%.