Tuesday-January 18th-2011-Statistics

Go to http://bcs.whfreeman.com/ips4e/cat_010/applets/confidenceinterval.html
Start off using a confidence level of 95%
Answer the following questions:

1. Click sample and take mental note of the length of CI.  Now change level to 99%.  How did length of CI change?
2. Do the same with levels 90% and 80%. 

The Pew Research council asked cell phone owners, "Have you ever received unsolicited text messages on your cell phone from advertisers?"  17% reported they had.  Pew estimates a 95% confidence interval to be 0.17+/-.04 or between 13% and 21%.  Are the following statements correct? Explain.

1. In Pew's sample, somewhere between 13% and 21% of respondents reported they had received unsolicited text messages. 
2. We can be 95% confident that 17% of US cell phone owners have received unsolicited advertising text messages.
3. We are 95% confident that between `13% and 21% of all US cell phone owners have received unsolicited advertising text messages.
4. We know between 13% and 21% of all US cell phone owners have received unsolicited advertising text messages.
5. 95% of all US cell phone owners have received unsolicited advertising text messages.