1
COURSE:
DSCI 3710
Print Name:
Exam 1
Signature:
Key
Summer 1 2010
Student ID#:
INSTRUCTIONS:
•
Please print your name and student ID number on this exam.
Also, put
your signature on this exam.
•
On your scantron PRINT your name and exam version.
•
You have
105 minutes
to complete this exam.
The exam is open book,
open notes, and open mind.
You may use any type of hand calculator but
please show all your work on the exam and mark all answers on the
scantron.
Usage of cell phones, digital cameras, PDAs, and other
communication devices is prohibited.
•
Please DO NOT pull this exam apart. When you have completed the
exam, please turn your scantron and exam booklet into your instructor, at
the front desk.
•
Good luck and we wish you well on the exam.
Note: Whenever question(s) are connected you may be asked to assume a
result (given a value) as an answer for the previous question but this result
(value) may or may not be correct.
The procedure is set in place to prevent
you from losing points on a subsequent question because you made a mistake
on some previous question/s.
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2
Use the information given in the following paragraph to answer next three
questions.
A lumber company is making 2x4s that are 11 feet long.
These 2x4s are being used to
make prefabricated homes.
If the 2x4s are too long they must be trimmed which results
in extra time and labor being expended, but if too short they can be used as is, by
supplying them to a children’s toy store.
A sample of 130 2x4s is made, and it is found
that they averaged 11.9 feet with a standard deviation of 0.04 feet.
Is there evidence, at
the 0.05 significance level, that the 2x4s are too long?
1.
What are the null hypothesis and alternative hypothesis for this test?
A.
Ho: μ = 11.9
Ha: μ
≠
11.9
B.
Ho: μ
≥
11.9
Ha: μ < 11.9
C.
Ho: μ = 11
Ha: μ
≠
11
D.
Ho: μ <
11
Ha: μ > 11*
E.
Ho: μ = 11
Ha: μ < 11
2.
What is the absolute critical value of the test statistic?
3.
Assuming the calculated value of the test statistic is +
1.83
, what are the decision and
conclusion of the test?
3
Use the information given below to answer the next question.
The production manager in a chemical plant knows that the time for a certain product line
to become stable after being stopped for machine adjustments is normally distributed.
He
uses a sample of 25 stoppages to determine a 95% confidence interval for the average
warmup period to be 11.3 to 19.7 minutes.
The firm
=
s cost accountant would like to
answer the following question: Is there sufficient evidence, at the 5% significance level,
to indicate that the average warmup period is different from 15 minutes?
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 Spring '08
 Dr.Jay
 Null hypothesis, Statistical hypothesis testing, Student's ttest

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