Example of Store Descriptive Statistics

A quality control engineer needs to ensure that the caps on shampoo bottles are fastened correctly. If the caps are fastened too loosely, they may fall off during shipping. If they are fastened too tightly, they may be too difficult to remove. The target torque value for fastening the caps is 18. The engineer collects a random sample of 68 bottles and tests the amount of torque that is needed to remove the caps.

As part of the initial investigation, the engineer stores the descriptive statistics of the torque measurements.

  1. Open the sample data, CapTorque.MTW.
  2. Choose Stat > Basic Statistics > Store Descriptive Statistics.
  3. In Variables, enter Torque.
  4. In By variables (optional), enter Machine.
  5. Click the Statistics button, and then select Standard deviation and deselect N nonmissing.
  6. Click OK.

Interpret the results

The mean torque value for Machine 1 is closer to the target of 18 than the value for Machine 2. The mean torque that is required to remove caps from Machine 1 is 18.6667. The mean torque that is required to remove caps from Machine 2 is 24.1875. The distribution of data from Machine 1 also is less variable. The standard deviation is 4.3948 for Machine 1, and is 7.11852 for Machine 2.

C1 C2 C3 C4 C5
Torque Machine ByVar1 Mean1 StDev1
24 2 1 18.6667 4.39480
14 1 2 24.1875 7.11852