The mean of 20 observations was 85, but later it was found that 97 was misread as 79. The correct mean is:
given that mean of 20 observations is 85
i.e;(sum of observations)/20=85
sum of observations=1700
but given that 97 was mis read as 79
therefore we need to add the value of 97-79=18
(sum of observations+18)/20 = correct mean
sum of observations=1700
therefore,
(1700+18)/20
=>85.9
therefore answer is optionC
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