A developer wants to know if the houses in two different neighborhoods were buil
ID: 3316416 • Letter: A
Question
A developer wants to know if the houses in two different neighborhoods were built at roughly the same time. She takes a random sample of six houses from each neighborhood and finds their ages from local records. The accompanying table shows the data for each sample (in years). Assume that the data come from a distribution that is Normally distributed.
Neighborhood 1
Neighborhood 2
49
41
45
47
52
56
47
35
60
37
53
54
a) Find a
95% confidence interval for the mean difference, 12, in ages of houses in the two neighborhoods.
Neighborhood 1
Neighborhood 2
49
41
45
47
52
56
47
35
60
37
53
54
Explanation / Answer
CI [1.16, 10.84].
Calculation
Pooled Variance
s2p = (SS1 + SS2) / (df1 + df2) = 88.04 / 8 = 11
Standard Error
s(M1 - M2) = ((s2p/n1) + (s2p/n2)) = ((11/5) + (11/5)) = 2.1
Confidence Interval
1 - 2 = (M1 - M2) ± ts(M1 - M2) = 6 ± (2.31 * 2.1) = 6 ± 4.84
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