Statistics: The mean and the standard deviation (S.D.) of five observations are… | JEE Main 2018 | Yukti Vault

Yukti Vault

JEE Main 2018 (Online) 16th AprilQuestion 1

The mean and the standard deviation (S.D.) of five observations are $9$ and $0$, respectively. If one of the observation is increased such that the mean of the new set of five observations becomes $10$, then their S.D. is

Statistics

$0$$2$✓ Correct answer$4$$1$

Solution

S.D. $0$ means all five equal $9$. New mean $10$ gives sum $50$, so one observation becomes $14$. Variance $=\frac{4\cdot1+16}{5}=4$, S.D. $=2$.

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