About the "No valid data" message

In order to create a control chart, you must have at least two consecutive nonmissing points for Minitab to calculate the standard deviation and draw the control chart.

When you try to create a control chart based on a subset of data, you may inadvertently exclude all the data.

For example, you may set the subset condition to exclude values > 50, but all values are greater than 50. Or, you may set the subset condition to include values from "Supplier A", but the worksheet does not contain any data from Supplier A.