Arandom sample of 49 text books purchased at a local bookstore showed an average price of $122 with a population standard deviation of $15. let u (new) be the true mean cost of a text book sold by this store. construct a confidence interval with a 90% degree of confidence. clearly label the following:
a. point estimate
b. critical value,
c. margin of error
d. confidence interval
e. interpretation (confidence statement).

point estimate is $122critical value for the 90% confidence level (1.645)margin of error is $3.52590% confidence interval is $122±3.525there is 90% probability that true population average price of text books is in the range $122±$3.525

Step-by-step explanation:

Confidence Interval can be calculated using P±ME where

P is the point estimate for the mean cost of a text book ( $122 )ME is the margin of error from the mean

And margin of error (ME) can be calculated using the formula

ME= where

z is the critical value for the 90% confidence level (1.645)s is the population standard deviation ($15) N is the sample size (49)

Margin of error, ME= = 3.525

Then 90% confidence interval is $122±3.525

To interpret this, there is 90% probability that true population average price of text books is in the range $122±$3.525