If the mean of m observations out of n observations is n and the mean of remaining observations is m, then what is the mean of all n observations?

Correct Answer: 2m \u2013m^2\/n

Mean of m observations is n

Mean of n-m observations is m

So total = nm+ (n-m)m

Total observations = n

Mean = Total / Total observations = (2mn-m^2)/n = 2m –m^2/n