The following example uses the data table. This quality characteristic of interest is the Weight 2 column. An X-chart and an S chart for the process are shown in X and S Charts for Varying Subgroup Sizes.
Select Help > Sample Data Library and open Quality Control/
Select Analyze > Quality and Process > Control Chart > XBar.
Select Weight 2 and click Process.
Select Sample and click Sample Label.
The Sample Size option should automatically change to Sample Grouped by Sample Label.
X and S Charts for Varying Subgroup Sizes
Weight 2 has several missing values in the data, so you might notice the chart has uneven limits. Although, each sample has the same number of observations, samples 1, 3, 5, and 7 each have a missing value.

Help created on 9/19/2017