The mean of the data

set is 15. What number

is missing?

18, 16, _,9,12, 23

The missing number is 12

Step-by-step explanation:

Step 1: Let the missing number be x. Mean = 15. Find x using the formula for finding mean

Mean = Sum of the observations/Total number of observations

Sum of observations = 18 + 16 + x + 9 + 12 + 23 = 78 + x

Number of observations = 6

⇒ 15 = 78 + x/6

⇒ 90 = 78 + x

⇒ x = 90 - 78 = 12