Statistics
Corrected Variance — Single Wrong Observation
nta_pyq_2023_apr
Grade 11
Question:
Mean and SD of 10 observations are 20 and 8. One observation was recorded as 50 instead of 40. Then the correct variance is
Step-by-Step Solution
Key Concept: Correct $\sum x_i=200-50+40=190$. New mean $=19$. Correct $\sum x_i^2=10(64+400)-2500+1600=4640-900=3740$. Variance $=\frac{3740}{10}-361=374-361=13$.
Correct variance $=13$.
Correct Answer: 2