According to a recent survey, high school girls average 100 text messages daily (The Boston Globe, 2010). Assume that the survey was based on a random sample of 36 high school girls. The sample standard deviation is computed as 10 text messages daily. (Round answers to 2 decimals.)
begin mathsize 24px style bold x with bold bar on top bold equals bold 100
bold italic s bold equals bold 10
bold italic n bold equals bold 36 end style
begin mathsize 24px style bold italic C bold italic a bold italic l bold italic c bold italic u bold italic l bold italic a bold italic t bold italic e bold space bold italic t bold italic h bold italic e bold space bold italic m bold italic a bold italic r bold italic g bold italic i bold italic n bold space bold italic o bold italic f bold space bold italic e bold italic r bold italic r bold italic o bold italic r bold space bold italic w bold italic i bold italic t bold italic h bold space bold 99 bold percent sign bold space bold italic c bold italic o bold italic n bold italic f bold italic i bold italic d bold italic e bold italic n bold italic c bold italic e bold. end style
Answer (2)
The margin of error for the average number of text messages sent daily by high school girls, calculated with 99% confidence, is approximately 4.29 messages. This is based on a sample standard deviation of 10 messages and a sample size of 36. The calculation uses the z-score for 99% confidence, which is about 2.576.
;
The margin of error with 99% confidence is approximately 4.29 text messages per day. ;
