Question

Researchers are interested in the texting habits of all US adults. A random sample of n=755 US cell phone users age 18 and older in May 2011 found that the average number of text messages sent or received per day is 41.5 messages, with standard error about 6.1. a)Because we did not take a census, we cannot give a specific value for the parameter, u. Instead, describe µ using words. Be very specific. b) What is our best estimate for µ? Use correct notation in your answer. c)Find a 95% confidence interval for the mean number of text messages. Use the 2*SE method. d) Interpret the interval you just formed. "We are_____% confident that the interval from_____to ______contains__________________________________________"

Answer 1

(a)

The population parameter (the average number of text messages sent or received per day of all US adults can be estimated as the mean of the sampling distribution of sample means of n = 755 US cell phone users age 18 and older in May 2011.

(b)

Best estimate for = Sample mean = = 41.5

(c)

So,

95% confidence interval :

Z SE

= 41.5 (2 X 6.1)

= 41.5 12.2

=(29.3 , 53.7)

(d)

We are 95% confident that the interval from 29.3 to 53.7 contains Population parameter .