A study of nickels showed that the the standard deviation of the weight of nickels is milligrams. A coin counter manufacturer wishes to find the 95% confidence interval for
The average weight of a nickel. How many nickels does he need to weigh to obtain an
Average accurate to within 20 milligrams?
A) 154
B) 57
C) 217
D) 306

Question

Quizplus · Accepted Answer

To find the sample size needed for a 95% confidence interval with a margin of error of 20 milligrams, we use the formula n = (Z*σ/E)^2, where Z is the Z-score for 95% confidence (approximately 1.96), σ is the standard deviation, and E is the margin of error. Solving this gives approximately 217 nickels.

A Study of Nickels Showed That the The Standard Deviation