Homework #2 (45 points)
STA 215: Introductory Applied Statistics
Name
Spring/Summer 2011
1. The weights of three adult males are (in pounds) 160, 215, and 195.
(a) Calculate the sample mean .
(1 point)
(b) Calculate the sample variance.
(4 points)
(c) The standard
error of the mean of these three weights is (
).
(2 points)
2. Scores on the SAT Mathematics test (SATM) are believed to be normally distributed
with mean
μ
. The scores of a random sample of three students who recently took the
exam are 550, 620, and 480. Calculate a 95% confidence interval for
.
(a) Calculate the sample mean .
(1 point)
(b) Calculate the sample variance.
(4 points)
(c) The standard
error of the mean of these three weights is (
).
(2 points)
(d) Calculate a 95% confidence interval for
.
(4 points)
3. Do students tend to improve their SAT Mathematics (SATM) score the second time
they take the test? A random sample of four students who took the test twice received
the following scores.
Student
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 Spring '11
 Statistics, Standard Deviation, Standard Error, Variance, 90%, SATM, 450 520 720 600 Second

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