A random sample of 120 classrooms at a large university found that 70% of them had been cleaned properly. What is the standard error of the sample proportion?
A) 0.042
B) 0.028
C) 0.458
D) 0.082
E) 0.046

Question

Quizplus · Accepted Answer

The standard error of the sample proportion is sqrt(p(1-p)/n), where p is the sample proportion and n is the sample size. In this case, p = 0.7 and n = 120, so the standard error is sqrt(0.7(1-0.7)/120) = 0.042.

A Random Sample of 120 Classrooms at a Large University