Homework # 13
Problem # 15 on Page 469
#15
HYPOTHESES
TEST STAT
(1) F = s1^2/s2^2
Required Condition:
Populations are approx Normal.
(2) If Ho is true
(var's equal), this ratio has a known "F" distribution with 2 df:
df1=n11
= 20
df2=n21
= 25
SIG LEVEL
Alpha = .05
REJECT RULE
Reject Ho if F:
<
0.4174
>
2.3005
CALCULATIONS
N1 =
21
N2=
26
S21 =
8.2
S22 =
4
F =
2.05
pvalue =
0.090
CONCLUSION
DO NOT REJECT HO
ANSWER
According to the sample results from the two samples
there is insufficent evidence to conclude the population
variances are different given the significance level of 5%
Even though there is a decent difference between the two
variances, there is not enough of a difference given the two
sample sizes to definitively be able to say they are different.
Example From Class Notes 22:
Issue:
Variability/consistency in service times for two bank tellers.
FTest
Suppose they had different training; we think teller 1's training might be better.
Bus Question:
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 Spring '07
 Dunne
 Statistics, Variance, Statistical hypothesis testing

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