THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION:
Suppose that 20% of all invoices are for amounts greater than $800.A random sample of 50 invoices is taken.
-What is the mean and standard error of the sample proportion of invoices with amounts in excess of $800?

Question

Quizplus · Accepted Answer

The mean of the sample proportion of invoices with amounts in excess of $800 is equal to the population proportion, which is 0.20. The standard error is calculated as the square root of [p(1-p)/n], where p is the population proportion and n is the sample size. Plugging in the values, we get SE = sqrt[(0.20)(0.80)/50] = 0.0566. Therefore, the correct answer is B.