A sample of n= 9 scores has a mean of M= 13. After one score is added, the mean is found to be M=12. What is the value of the score added?
- UserLv 71 month ago
>> A sample of n= 9 scores has a mean of M= 13 <<
(9 * mean score)/9 = 13
(obviously, mean score = 13)
>> After one score is added, the mean is found to be M=12 <<
((9 * 13) + x)/10 = 12
What I've done:
you count all of the 9 existing scores as if they were the same as the mean score
and then add the new score
in the equation for calculating the new mean
and solve for the new score.
Just solve that last equation for "x" and you will get the correct answer.