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BES220 Semester Test 2 2020
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14/10/2020 Semester test 2Semester test 2
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Question Number
Question 1
Question 2
Question 3
Question 4
Performance Summary
Exam Name: Semester test 2
Session ID: 0448463074
Student's Name: K (Katarina) Djordjevic (011cdd57506642ec949f60ac53aa58da)
Exam Start: Wed Oct 14 2020 07:30:19
Exam Stop: Wed Oct 14 2020 08:53:56
Time Spent: 1:23:36
Question 1
Answer the following multiple-choice questions.
1.
Quality control engineers are testing two di erent light bulbs, designed to have a
lifetime of more than 450 hours. 97 of the first type of light bulbs were tested and
0.35% of them have a lifetime of more than 450 hours. 144 of the second type of light
bulbs were tested and 0.57% of them have a lifetime of more than 450 hours. The
engineers want to conduct a hypothesis test to test if there is a di erence in the quality
of the bulbs.
https://numbas.up.ac.za/run_attempt/87074?resource_link_id=_2040073_1 1/11
, 14/10/2020 Semester test 2
What is the Standard Error for the hypothesis test?
0.0636 0.0413 0.0656 0.0484
2 marks
2.
According to a report on sleep deprivation by the Centers for Disease Control and
Prevention, the proportion of California residents who reported insu icient rest or
sleep during each of the preceding 30 days is 0.079%, while this proportion is 0.091%
for Oregon residents. These data are based on simple random samples of 11112
California and 4686 Oregon residents. Calculate a 95% confidence interval for the
di erence between the proportions of Californians and Oregonians who are sleep
deprived and interpret it in the context of the data. Assume that all conditions are
satisfied.
(0.00,0.95) (0.0024,0.0216) (0.079,0.091)
(-0.0216,-0.0024)
2 marks
3.
Approximately 0.09% of engineering students in South Africa are women. To test
whether our university di ers significantly from this national average, we take a
random sample of 40 engineering students at our university and find that 9 are female.
Calculate the appropriate test statistic to determine whether our university di ers
significantly from the national rate.
2.9835 2.0447 0.0452 -2.0447 0.225
2 marks
https://numbas.up.ac.za/run_attempt/87074?resource_link_id=_2040073_1 2/11
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