When a cell doesn't contain any data and is between other cells that do contain data, it is called a missing value. However, empty cells at the end of columns are not considered missing values.
When a value is missing from a column of numeric or date/time data, Minitab denotes it with an asterisk. When a value is missing from a column of text data, Minitab denotes it with the word "Missing".
If your data uses "-99" or some other value to identify missing values, you can useto change those values to asterisks. If you do not change the values, errors can occur in analyses that use the data.