standard deviation

[Target MA]

The distribution of the heights of students in a large class is roughly bell shaped. Moreover,
the average height is 68 inches, and approximately 95% of the heights are between 62 and 74
inches. What is the standard deviation of the height distribution approximately?
a) 2 c) 6
b) 3 d) 9

[MI]

Roughly 95 % of heights lie in the interval  (u - 2*sigma , u+ 2*sigma).

Here 2* sigma = 6

=> sigma = 3

[Target MA]

how did you get 2*sigma=6 ?

[MI]

as u=68

and its given that 95% of values are between 62 and 74

(62, 74) interval corresponds to ( u - 2*sigma, u + 2*sigma)

[Target MA]

ya got it...thanx