Question

A toy manufacturer wants to know how many new toys children buy each year. A sample of 1492 children was taken to study their purchasing habits. Construct the 99% confidence interval for the mean number of toys purchased each year if the sample mean was found to be 8.8. Assume that the population standard deviation is 2.2. Round your answers to one decimal place.

Answer 1

By assuming the standard deviation of population 2.2 the confidence interval is 8.67 toys,8.94 toys.

Given sample size of 1492 children,99% confidence interval , sample mean of 8.8, population standard deviation=2.2.

This type of problems can be solved through z test and in z test we have to first find the z score and then p value from normal distribution table.

First we have to find the value of α which can be calculated as  under:

α=(1-0.99)/2=0.005

p=1-0.005=0.995

corresponding z value will be 2.575 for p=0.995 .

Margin of error=z*x/d

where x is mean and d is standard deviation.

M=2.575*2.2/$\sqrt{1492}$

=0.14

So the lower value will be x-M

=8.8-0.14

=8.66

=8.67 ( after rounding)

The upper value will be x+M

=8.8+0.14

=8.94

Hence the confidence interval will be 8.67 toys and 8.94 toys.

Learn more about z test at brainly.com/question/14453510

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