Question

Mean of $25$ observations was found to be $78.4$. But later on it was found that $96$ was misread $69$. The correct mean is

• A. 79.24
• B. 79.48
• C. 80.1
• D. None of these

Answer 1

Answer: (B)

79.48

Answer 2

Mean $\bar{x}=\frac{\sum x}{n}$ or $\sum x=n \bar{x}$ $\sum x=25 \times 78.4=1960$ But this $\sum x$ is incorrect as 96 was misread as $69 .$ $\therefore$ correct $\sum x=1960+(96-69)=1987$ $\therefore$ correct mean $=\frac{1987}{25}=79.48$ $\therefore$ correct $\sum x=1960+(96-69)=1987$ $\therefore$ correct mean $=\frac{1987}{25}=79.48$