Question #1
It has been computed that the 95% confidence interval
is [144.4, 154.2] for the average
exam score when a student spent 10 hours on average per week studying for the class.
The 90% prediction interval
for a student who spent 10 hours on average per week
studying for the class will be
•
narrower
•
wider
•
cannot be determined based on the provided information.
•
of the same width
You received a raw score of 100% on this question.
Question #2
It has been computed that the 95% confidence interval
is [144.4, 154.2] for the average
exam score when a student spent 10 hours on average per week studying for the class.
The 99% prediction interval
for a student who spent 10 hours on average per week
studying for the class will be
•
of the same width
•
narrower
•
wider
•
cannot be determined based on the provided information.
You received a raw score of 100% on this question.
Question #3
Now do the examples described in slides 57 and 58 (page 91) of the course packet.
Notice, however, that here you are given actual data and the results will differ than those
in your course packet. The necessary data is
here
.
You are asked to provide an interval estimate for the bidding price on a Ford Taurus with
40,000 miles on the odometer. The 95% prediction interval for the price of a single car
with 40,000 miles is
[
13968.61756 = 13968.61756
,
15179.67638 = 15179.67638
].
Now the dealer wants to bid on a lot of Ford Tauri, where each car has been driven
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40,000 miles. The 95% confidence interval is
[
14503.76183 = 14503.76183
,
14644.53212 = 14644.53212
].
Item 1:
Your answer is within ±0.1% of the solution  correct.
Item 2:
Your answer is within ±0.1% of the solution  correct.
Item 3:
Your answer is within ±0.1% of the solution  correct.
Item 4:
Your answer is within ±0.1% of the solution  correct.
You received a raw score of 100% on this question.
Question #4
Now do the examples described in slides 59 and 60 (page 91) of the course packet. First
run a regression and then calculate the predicted value, yhat, for x=35, and then make
the prediction interval and the confidence interval. The data is provided
here
.
The LOWER BOUND of the prediction interval is
285.895 = 285.895
and the
UPPER BOUND of the confidence interval is
388.797 = 388.797
.
Item 1:
Your answer is within ±0.1% of the solution  correct.
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 Spring '08
 Petry
 Normal Distribution, Regression Analysis, Errors and residuals in statistics, raw score

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