How to interpret missing values in a table

By default, Minitab displays all missing values in your tables, but does not include them in calculations unless you check Include displayed missing values in calculations in the Options sub-dialog box. When a data point is missing, by default, the entire worksheet row (observation) is omitted from the calculation. You have to decide which statistic is more meaningful for your application. If any part of the data for an individual is missing, some researchers would eliminate the entire point from the study, while others would use the data they can.

In this example, for Stat > Tables > Descriptive Statistics, you are missing eye color data for 1 female and 2 males.

Tabulated Statistics: Gender, Eyecolor

Rows: Gender Columns: Eyecolor Blue Brown Green Hazel Missing All F 124.2 123.3 118.0 125.0 120.0 122.2 19.25 10.63 13.40 18.03 * 15.06 7 5 7 5 1 24 14.89 10.64 14.89 10.64 * 51.06 M 156.3 159.1 156.8 164.7 170.0 158.4 28.47 13.91 20.77 10.02 * 20.12 8 8 4 3 2 23 17.02 17.02 8.51 6.38 * 48.94 All 142.5 146.1 132.1 139.9 * 140.3 29.16 21.86 24.89 25.22 * 25.36 15 13 11 8 * 47 31.91 27.66 23.40 17.02 * 100.00 Cell Contents Weight : Mean Weight : Standard deviation Count % of Total

Do not include missing values in calculations (Default)

If you do not include missing data in your calculations, the mean weight of females in your study is 122.2 pounds, which does not include the females whose eye color was missing from the data. For males, the mean weight is 158.4 pounds, which does not include the males whose eye color was missing from the data. Also, when you do not include the missing values, the count is 24 females (51.06%) and 23 males (48.94%) in the study.

Tabulated Statistics: Gender, Eyecolor

Rows: Gender Columns: Eyecolor Blue Brown Green Hazel Missing All F 124.2 123.3 118.0 125.0 120.0 122.1 19.25 10.63 13.40 18.03 * 14.72 7 5 7 5 1 25 14 10 14 10 2 50 M 156.3 159.1 156.8 164.7 170.0 158.9 28.47 13.91 20.77 10.02 * 19.80 8 8 4 3 2 25 16 16 8 6 4 50 All 142.5 146.1 132.1 139.9 145.0 140.5 29.16 21.86 24.89 25.22 35.36 25.36 15 13 11 8 3 50 30 26 22 16 6 100 Cell Contents Weight : Mean Weight : Standard deviation Count % of Total

Include missing values in calculations

If you include the weight data when eye color is missing, the mean weight for females is 122.1 pounds. For males, the mean weight is 158.9 pounds when missing data are included. When you include the missing values, the count is 25 females (50%) and 25 males (50%) in the study.