Question:

Mean and SD of 10 students are 50 and 12. Two marks 20 and 25 were wrongly read as 45 and 50. Then the correct variance is

Step-by-Step Solution

Key Concept: Correct $\sum x_i=500-45-50+20+25=450$. New mean $=45$. Correct $\sum x_i^2=\sum x_i^2-45^2-50^2+20^2+25^2$.

Correct variance $=269$.

Correct Answer: 269