18.2 Graph of Individual Observations

Create a graph for the 32 samples of the pH values (file CHLORINE.MTW) obtained in the last day. To achieve that, first, separate the values which correspond to that last day (which is a Friday; that is why we add an ‘F’ at the end of the variable names in the new columns). This is done by copying the selected columns, as follows.

Data > Copy > Columns to Columns

nc18uf001.eps
Remember: Just write the names of the new columns and Minitab will create them in the first empty position.
If the name of the new columns contains blank spaces, it must be enclosed in single quotes: ‘Time F’.

Stat > Control Charts > Variables Charts for Individuals > Individuals

nc18uf002.eps

Use all default options to obtain:

nc18uf003.eps

Get Industrial Statistics with Minitab now with O’Reilly online learning.

O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers.