Question 71

The mean height of 30 students was given as 140 cm. It was later observed that one of the observations was incorrectly copied as 121 cm while it was actually 134 cm. What was the correct mean height? [Give your answer correct to one place of decimal.]

Solution

The mean height of 30 students was given as 140 cm.

Total height of 30 students initially = $$140\times30$$ = 4200

It was later observed that one of the observations was incorrectly copied as 121 cm while it was actually 134 cm.

Correct mean height = $$\frac{4200-121+134}{30}$$

= $$\frac{4213}{30}$$

= 140.433333

= 140.4 cm

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