Question

The mean of 8 observations is 25. The 7 observations are 30, 24, 27, 22, 18, 26, 32. What is the 8^th observation?
1. 20
2. 21
3. 22
4. 23

Answer 1

Correct Answer - Option 2 : 21

Concept:

Mean of n elements = \(\rm \text{Sum of all n elements}\over\text{Total number of elements (n)}\)

Calculation:

Let the missing number be x

Given Mean = 25, Total elements = 8

\(\rm 30+24+27+22+18+26+32+x\over 8\) = 25

179 + x = 200

x = 21