#### The sum of 100 observations and the sum of their squares are 400 and 2475, respectively.  Later on, three observations, 3, 4 and 5, were found to be incorrect.  If the incorrect observations are omitted, then the variance of the remaining observations is : Option 1) 8.25 Option 2) 8.50 Option 3) 8.00 Option 4) 9.00

As we learnt in

ARITHMETIC Mean -

For the values x1, x2, ....xn of the variant x the arithmetic mean is given by

in case of discrete data.

-

Short cut Method for Variance -

In case of discrete frequency distribution

-

Omitting 3, 4, 5 we get

Sum of squares = 2475-50=2425

Variance =

=25-

Option 1)

8.25

This option is incorrect

Option 2)

8.50

This option is incorrect

Option 3)

8.00

This option is incorrect

Option 4)

9.00

This option is correct

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