When you select a record, its statistics are displayed in the Attribute Manager. You can choose the statistics you want to display.
In the Attribute Manager, click Edit and then click Preferences.
In the Preferences window, enable any of the following check boxes in the Field Statistics area:
Count: displays the number of selected records
Sum: calculates the sum of the values for the selected records for each numeric field
Mode: calculates the value that occurs the most frequently among the selected records for each field
Mean: calculates the average value of the selected records for each numeric field. The average is obtained by adding values of the selected records and dividing that value by the number of records used in the sum.
Minimum: displays the lowest value in the numeric field from the selected records
Median: ranks for each numeric field the values of the selected records in numerical order. The median is the middle value of the selected records.
Maximum: displays the highest value in the field from the selected records
Standard Deviation: measures the variation in the distribution of values, which is calculated from square root of the variance