Having calculated the sum of all the subgroup means, we can now calculate the grand mean, by divding the sum by the number of subgroups. Looking at your printed chart, you will see that there are 25 subgroups. This value has already been entered into the second box for you.
Because the subgroup means are rounded to the nearest whole number, the grand mean should be calculated to 1 decimal place. Complete the calculation, and enter the result into the box outlined in red below. When you have done this, click the button to check your answer.