Worksheet 5 9/03/08
Problem 1. Before they attend college, every Martian takes the MAT (Martian Aptitude
Test). An SRS of Martian high school students is collected, and the results are below:
33.2 31.9 32.6 26.5 33.3
32.3 33.0 32.0 30.5 32.7
23.0 30.9 32.7 33.7 32.3
24.1 30.2 31.3 28.7 31.9
The population standard deviation of MAT scores is σ= 3.
(a) We know for the SAT, that the scores are approximately normal. From this sample,
does it appear that MAT scores are also approximately Normally distributed? Make a
stemplot to check.
(b) Assuming that it is in fact Normal, calculate a 90% confidence interval for the mean
MAT score.
(c) What size sample do we need to collect to get the margin of error down to .5?
