Question

The mean of 100 observation was found to be 30. If two observation were wrongly taken as 25 and 13 instead of 24 and 12 , find the correct mean

• A. 39.98
• B. 29.98
• C. 35.23
• D. 30

Answer 1

The correct option is B

29.98

Mean = $\frac{\text{Sum of total observation(x)}}{\text{Total Observation(n)}}$

Given Mean = 30

Number of observation = 100

Sum of total observation = 3000

Incorrect value of $x$ = 3000
Correct value of $x$ = 3000 - (25 + 13) + ( 24 + 12)
= 3000 - 38 + 36
= 2998

Correct Mean = $\frac{\text{Correct value of x}}{\text{Number of Observation}}$

= $\frac{2998}{100}$
= 29.98