Find the population standard deviation of the following frequency distribution.

Score Frequency

1 9

2 15

3 6

total=30

so, 1*9+2*15+3*6=57

57/30=1.9

and, 9(1-1.9)^2+15(2-1.9)^26(3-1.9)^2=14.7

14.7/30=sqr.49 sqr.49 is my answer, list of possible answers are -

1.sqr0.49

2.sqr1.9

3.sqr2.0

4.sqr2,2

thanks for checking