A random sample of 25,000 ACT test takers had an average score of 21 with a standard deviation of 5. With a .95 probability, determine the margin of error.
A) .0277
B) .0568
C) .2603
D) .0620

Question

Quizplus · Accepted Answer

We can use the formula for margin of error:
Margin of Error = z*(standard deviation/square root of sample size)
For a 95% confidence level, the z-score is 1.96. 
So, Margin of Error = 1.96*(5/sqrt(25000)) = 0.062 or 0.0620 (rounded to 4 decimal places) which is option D.

A Random Sample of 25,000 ACT Test Takers Had an Average