Question

A researcher is interested in finding a 90% confidence interval for the mean number minutes students are concentrating on their professor during a one hour statistics lecture. The study included 128 students who averaged 42.3 minutes concentrating on their professor during the hour lecture. The standard deviation was 10.7 minutes. Round answers to 3 decimal places where possible.

a. To compute the confidence interval use a _____ (t? or z?) distribution.

b. With 90% confidence the population mean minutes of concentration is between ______ and ______ minutes.

c. If many groups of 128 randomly selected members are studied, then a different confidence interval would be produced from each group. About _____ percent of these confidence intervals will contain the true population mean minutes of concentration and about _____ percent will not contain the true population mean minutes of concentration.

g on their professor during a one hour statistics lecture. The study included 128 students who averaged 42.3 minutes concentrating on their professor during the hour lecture. The standard deviation was 10.7 minutes. Round answers to 3 decimal places where possible.

Answer 1

( a )

use a t distribution.

( b )

With 90% confidence the population mean minutes of concentration is between 40.733 and 43.867 minutes.

( c )

About 90  percent of these confidence intervals will contain the true population mean minutes of concentration and about 10   percent will not contain the true population mean minutes of concentration.