Warranty Analysis Usage Format Example

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This example appears in the Life Data Analysis Reference book.


Warranty Analysis Usage Format Example

Suppose that an automotive manufacturer collects the warranty returns and sales data given in the following tables. Convert this information to life data and analyze it using the lognormal distribution.

Quality In-Service Data
Quantity In-Service Date In-Service
9 Dec-09
13 Jan-10
15 Feb-10
20 Mar-10
15 Apr-10
25 May-10
19 Jun-10
16 Jul-10
20 Aug-10
19 Sep-10
25 Oct-10
30 Nov-10


Quality Return Data
Quantity Returned Usage at Return Date Date In-Service
1 9072 Dec-09
1 9743 Jan-10
1 6857 Feb-10
1 7651 Mar-10
1 5083 May-10
1 5990 May-10
1 7432 May-10
1 8739 May-10
1 3158 Jun-10
1 1136 Jul-10
1 4646 Aug-10
1 3965 Sep-10
1 3117 Oct-10
1 3250 Nov-10


Solution

Create a warranty analysis folio and select the usage format. Enter the data from the tables in the Sales, Returns and Future Sales sheets. The warranty data were collected until 12/1/2010; therefore, on the control panel, set the End of Observation Period to that date. Set the failure distribution to Lognormal, as shown next.

Usage In-Service Weibull Data.png

In this example, the manufacturer has been documenting the mileage accumulation per year for this type of product across the customer base in comparable regions for many years. The yearly usage has been determined to follow a lognormal distribution with [math]{{\mu }_{T\prime }}=9.38\,\![/math], [math]{{\sigma }_{T\prime }}=0.085\,\![/math]. The Interval Width is defined to be 1,000 miles. Enter the information about the usage distribution on the Suspensions page of the control panel, as shown next.

Specify Usage Distribution.png

Click Calculate to analyze the data set. The parameters are estimated to be:

[math]\begin{align} & {{\mu }_{T\prime }}= & 10.528098 \\ & {{\sigma }_{T\prime }}= & 1.135150 \end{align}\,\![/math]

The reliability plot (with mileage being the random variable driving reliability), along with the 90% confidence bounds on reliability, is shown next.

Usage Example Reliability Plot.png

In this example, the life data set contains 14 failures and 212 suspensions spread according to the defined usage distribution. You can display this data in a standard folio by choosing Warranty > Transfer Life Data > Transfer Life Data to New Folio. The failures and suspensions data set, as presented in the standard folio, is shown next (showing only the first 30 rows of data).

Usage Example Weibull Std Folio Data.png