Question

Correct answer is 751.67. Please show how you got everything! No shortcuts! How did you get Z? If can, please show how you do it on a Ti-84 calculator?

A previous study of nickels showed that the standard deviation of the weight of nickels is 250 milligrams. A coin counter manufacturer wants to estimate the mean weight to within 15 milligrams with 90% confidence. How many nickels does he need to weigh?

Answer 1

Confidence level = c = 0.90

Level of significance = = 1 - c = 1 - 0.90 = 0.10

c + = 0.90 + 0.05 = 0.95

We have to find value of z using Ti-84 calculator.

The path is Click on 2ND --------> VARS ----------> invNorm( -------->

area: 0.95

: 0

: 1

Paste

We get

z = 1.64

Now we have to find value of sample size (n)

Margin of error = E = 15

Population standard deviation = = 250

We have to find sample size (n)