The arithmetic mean of the observations 28, 31, 40, 63, 57, 37, 34, 70 and 99 is:

Correct option is D

Given:

Observations: 28, 31, 40, 63, 57, 37, 34, 70, 99

Formula Used:
Arithmetic Mean $$=\dfrac{\text{Sum of observations}}{\text{Number of observations}}$$​​

Solution:
Sum = 28 + 31 + 40 + 63 + 57 + 37 + 34 + 70 + 99 = 459
Number of observations = 9
Mean =$$\dfrac{459}{9}=5$$​1