Question

The marks obtained by 9 students in a test of 100 marks in Mathematics are given below:

64, 63, 72, 65, 68, 69, 66, 67, 69

Find the standard deviation of marks obtained by the students.

Answer 1

Here n = 9

Mean:

x̄ = \(\frac{Σx}{n}=\frac{603}{9}\) = 67 marks

Standard deviation of marks:
s = \(\sqrt\frac{Σ(x−\bar x)^2}{n}\)
= \(\sqrt\frac{64}{9}\)
= \(\sqrt{7.111}\)
= 2.67 marks