## A researcher wants to determine whether there is a relationship between age and the number of text messages sent in a given day. In a

A researcher wants to determine whether there is a relationship between age and the number of text messages sent in a given day. In a random sample of 18- to 25-year-old cell phone users, 100 of 125 users sent texts more often than they made phone calls. In a random sample of 26- to 35-year-old cell phone users, 75 of 120 sent texts more often than they made phone calls. What is the margin of error for a 99% confidence interval for the difference between the proportions of cell phone users in these age groups who text more often than they call?

a. 0.0032

b. 0.0569

c. 0.1114

d. 0.1465

e. 0.2864

## Answers ( )

Answer:The best option would be:

d. 0.1465

Step-by-step explanation:Previous conceptsA

confidence intervalis “a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval”.The

margin of erroris the range of values below and above the sample statistic in a confidence interval.Normal distribution, is a “probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean”.represent the real population proportion for brand 18-25 users

represent the estimated proportion for 18-25 users

is the sample size

represent the real population proportion for 26-35 users

represent the estimated proportion for 26-35 users

is the sample size required for Brand B

represent the critical value for the margin of error

The population proportion have the following distribution

Solution to the problemThe confidence interval for the difference of two proportions would be given by this formula

For the 99% confidence interval the value of and , with that value we can find the quantile required for the interval in the normal standard distribution.

And the margin of error is given by:

And if we replace we got:

The best option would be:

d. 0.1465