A 95% confidence interval for a population mean is determined to be 100 to 120. If the confidence coefficient is reduced to 0.90, the interval: a. becomes narrower b. becomes wider c. does not change d. becomes 0.1

  (1)

The confidence interval for this case would be:

And we want to know what happens with the interval if we reduce the confidence level to 90% and for this case we will get a narrower interval since the critical value would be lower. So then the best option would be:

a. becomes narrower

Step-by-step explanation:

Notation

represent the sample mean for the sample  

population mean

s represent the sample standard deviation

n represent the sample size  

Solution

The confidence interval for the mean is given by the following formula:

  (1)

The confidence interval for this case would be:

And we want to know what happens with the interval if we reduce the confidence level to 90% and for this case we will get a narrower interval since the critical value would be lower. So then the best option would be:

a. becomes narrower

a.   since the profit made in 2012 is equal to the profit made in 2014, the profit is symmetric about the line y = 120,000.

step-by-step explanation:

step-by-step explanation: