Question

The mean of 10 observations is 15. If one observation 15 is added, then the new mean is

(a) 16 (b) 11 (c) 10 (d) 15

Answer 1

Sum of 10 observations = 10 $\text{×}$ 15 = 150
Sum of 11 observations = 150 + 15 = 165
Number observations = 11
Mean of 11 observations = $\frac{165}{11}=15$
Thus, the new mean is 15.
Hence, the correct option is (d).