What is the standard deviation (s) for this set of data? 24, 18, 21, 28

A) 4.27
B) 22.75
C) 18.25
D) 3.70

To calculate the standard deviation, we first need to find the mean:

Mean = (24+18+21+28)/4 = 22.75

Next, we need to find the variance:

Variance = [(24-22.75)^2 + (18-22.75)^2 + (21-22.75)^2 + (28-22.75)^2]/4

Variance = 16.1875

Finally, we take the square root of the variance to get the standard deviation:

s = sqrt(16.1875) = 4.27

Therefore, the answer is A) 4.27.