2019 · Q68
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?
Elementary MathematicsStatistics
- A2m - m²/n
- B2m + m²/n
- Cm - m²/n
- Dm + m²/n
Explanation
Sum of the m observations = mn; sum of the remaining n−m = (n−m)m. Total = 2mn − m^2, so the mean of all n is (2mn − m^2)/n = 2m − m^2/n.