The city's PR manager was wrong because the mean score of all ninth graders in the city is 83.
Explanation:
The given observations are:
81, 96 and 72
The total number of observations = 3
We know that,
Mean =



= 83
∴ The mean score of all ninth graders in the city = 83
The city's PR manager was wrong because the mean score of all ninth graders in the city is 83.