I think the answer is Letter C - 0.032.
Given: p - 0.1; n - 90
Required: standard deviation of the sample proportion
Solution: To get the standard deviation of the sample proportion, we will use this formula - std = √p (1 - p) / n Replace the variables with the given values, then simplify.
std = √0.1 (1 - 0.1) / 90
std = √0.09 / 90
std = √0.001
std = 0.032