2-Sample t for Improve Stock Rotation

Use 2-Sample t to demonstrate that average stock rotation time decreases after a process improvement.

This example applies to the Supply Chain Module. For more information, go to www.minitab.com/supply-chain-module.

Example

Stock rotation is the number of days until the inventory stock is depleted. To calculate stock rotation, first divide the average inventory value by the total sales for the same time period. Then multiply this ratio by the number of days in the time period.

In this worksheet, Turnover Days contains the stock rotation times. Process Change indicates whether the stock rotation times are before or after a process improvement.

C1	C2-T
`Turnover Days`	`Process Change`
48.8	Before
49.9	Before
63.1	Before
40.8	After
37.5	After
43.7	After

How-to

Choose Solutions Modules > Functions > Supply Chain KPIs, then select Launch.
Under Inventory, select Stock rotation.
Select Improve stock rotation, then click OK.
Select 2-Sample t, then click OK.
From the drop-down list, select Both samples are in one column.
In Samples, enter the column that contains the stock rotation data.
In Sample IDs, enter the column that indicates whether the data are from before or after your process improvement.
Click Options. In Alternative hypothesis, select Difference > hypothesized difference. The hypothesized difference defines your null hypothesis. By default, the hypothesized difference = 0. This one-sided test has greater power to detect whether the stock rotation time has decreased after the process change.
Click OK.

Tip

For more information about this analysis, click Help in the main dialog box.