Question

The population standard deviation for the heights of dogs in inches in a city is 3.9...

The population standard deviation for the heights of dogs in inches in a city is 3.9 inches. If we want to be 90% confident that the sample mean is within 2 inches of the true population mean. What is the minimum sample size that can be taken?

Z0.10

1.282

Z0.05

1.645

Z0.025

1.960

Z.0.01

2.326

Z0.005

2.576

Homework Answers

Answer #1

Solution :

Given that,

Population standard deviation = = 3.9

Margin of error = E = 2

At 90% confidence level the z is ,

= 1 - 90% = 1 - 0.90 = 0.10

/ 2 = 0.10 / 2 = 0.05

Z/2 = Z0.05 = 1.645

sample size = n = (Z/2* / E) 2

n = (1.645 * 3.9/ 2)2

n = 10.2897

n = 11

Sample size = 11

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