STA 6126
Fall 2006
Exam 2
PRINT Name ____________
A research article conducts a significance test to determine whether the mean food
expenditures differ among families in two societies.
Their 95% Confidence Interval
for
μ
2
μ
1
is (32 , 48). Which of these statements best describes the Pvalue for testing
H
0
:
μ
2
μ
1
= 0 vs
H
A
μ
2
μ
1
≠
0:
a) Pvalue < 0.05 (Equivalence of CI and 2sided test)
b)
Pvalue
≥
0.95
c)
PValue
≥
0.05
d)
We need more information to obtain the Pvalue
Two graduate students obtain individual random samples of members of the Graduate
Student Union at their large university. They ask each sampled student whether they
favor a candidate for the president of their union. Satchel samples 100 students, of which
45 favor the candidate. Lee samples 200 students, of which 110 favor the candidate.
Whose 95% confidence interval for the true proportion of all graduate students will be
narrower (more precise)
? Why? Assume that the university has over 10,000 graduate
students so that the sample sizes are negligible relative to the population.
a)
Satchel’s because of a lower sample size
b) Satchel’s because of a lower proportion
c)
Lee’s because of a higher sample size (see formula for std error)
d)
Lee’s because of a higher proportion
e)
They will be the same, since .45(1.55) = .55(1.45)
For a largesample test of H
0
:
μ
= 0 vs H
A
:
μ
< 0, the
z
test statistic is 0.40. Give the
Pvalue:
a)
.8446
b) .6554 (P(z)<.40, lower tailed test)
c)
.6892
d)
.3446
A study is being conducted to determine whether a new formulation of whitening
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 Spring '08
 YESILCAY
 Statistics, Statistical hypothesis testing

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