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Stat 3011
Homework 8
Stat 3011: Homework 8
Due:
Tuesday, March 31st
Directions:
See the homework website for general directions.
Assigned Exercises:
1. 8.28 (page 383)
(a) book part a (Recall that the standard error is
s/
√
n
.)
(b)
Show
that the 95% conﬁdence interval for
μ
, the true mean ideal number of kids for
males, is (2.94, 3.17).
(c)
Interpret
the conﬁdence interval from part b.
2. 8.30 (page 383) Directions for Rweb are given on the next page.
(a) Use Rweb to create a stemandleaf plot of the weight change data.
(b) Check the two assumptions needed for the conﬁdence interval. Does it appear that they
hold?
(c) Use Rweb to calculate
x
, the sample mean, and
s
, the sample standard deviation for
the weight change data.
(d) Use your answers to part c to calculate a 95% conﬁdence interval for
μ
, the true popu
lation mean change in weight for family therapy.
(e) Use the “t.test” function in Rweb to verify your answer to part d.
(f) Explain why the interval in part d suggests that the true mean change in weight is
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 Spring '09
 WANG,ZHAN
 Standard Error

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