Question

The mean of 10 observations was calculated as 45 . It was detected on rechecking that the value of 40 was wrongly copied as 10 .Find the correct mean .​

Answer 1

Answer:

Mean = (Sum of all observations)/(Number of observations) or, 40 = (Sum of all observations)/10 So, sum of all observations = 400 But this is incorrect sum, since one observation was copied wrongly. So, correct sum = Incorrect sum – Incorrect observation + correct observation = 400 – 15 + 45 = 430 Correct Mean = Correct Sum/ Number of observations = 430/10 = 43

Answer 2

Here,

n=40,

X

=160

So,

X

=

n

1

(∑x

i

)

160=

40

1

(∑x

i

)

∑x

i

=6400

Therefore, incorrect value of ∑x

i

=6400

Now,

Correct value of ∑x

i

=6400−125+165=6440

Therefore,

Correct mean =

40

6440

=161

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