Question

The mean and standard deviation of marks obtained by 50 students of a class in three subjects, mathematics, physics and chemistry are given below :

Subject	Mathematics	Physics	Chemistry
Mean	42	32	40.9
Standard deviation	12	15	20

Which of the three subjects shows the highest variability in marks and which shows the lowest?

Answer 1

σ_m = 12,σ_p = 15,σ_m = 20 and \(\bar{X_m}\) = 42, \(\bar{X_p}\) = 32, \(\bar{X_c}\) = 40.9

Coefficient variability = \(\frac{\sigma}{\bar{x}}\times100\)

Cv (Maths) = \(\frac{12}{42}\times 100\)

Cv (Maths) = 28.57 

Cv (physics) = \(\frac{15}{32}\times100\)

So, Cv (physics) = 46.87 

Cv (chemistry) = \(\frac{20}{40.9}\times 100\) 

So, Cv (chemistry) = 48.89 

Hence, Cv of chemistry is greatest, the variability of marks in chemistry is highest and that of Mathematics is lowest.