Stat 124 Assignment 9 2018W2 Due: Your last lecture to Dr. Han
Question 1
MacInTouch reported that several versions of the iPod reported failure rates of 20% or more. From a customer survey, the colour iPod, first released in 2004, showed 64 failures out of 517. Is there any evidence that the failure rate for this model may be lower than the 20% rate of previous models? (7 points)
Question 2
A survey of 1000 workers indicated that approximately 520 have invested in an individual retirement account. National data suggest that 44% of workers invest in individual retirement accounts.
(a) (4 points) Create a 95% confidence interval for the proportion of workers who have in- vested in individual retirement accounts based on the survey.
(b) (7 points) Does this provide evidence of a change in behaviour among workers? (i.e., is the proportion different from 44%?)
Question 3
11% of 1,001 Americans responding to a 2006 Gallup survey stated that they have objections to celebrating Halloween on religious grounds. At a 95% confidence level, the margin of error for this survey is ¡À3%. A news piece on this study¡¯s findings states: ¡°More than 10% of all Americans have objections on religious grounds to celebrating Halloween.¡± At a 95% confidence level, is this news piece¡¯s statement justified? (6 points)
Question 4
An airline¡¯s public relations department says that the airline rarely loses Passengers¡¯ luggage. It further claims that on those occasions when luggage is lost, 90% is recovered and delivered to its owner within 24 hours. A consumer group who surveyed a large number of air travellers found that only 103 of 122 people who lost luggage on that airline were reunited with the missing items by the next day (within 24 hours). Does this cast doubt on the airline¡¯s claim? (7 points)
Question 5
A company is criticized because only 13 of 43 people in executive-level positions are women. The company explains that although this proportion is lower than it might wish, it¡¯s not surprising given that only 40% of all their employees are women. What do you think? Verify if the conditionis satisfied. Test an appropriate hypothesis and state your conclusion. (8 points)
Question 6
The General Social Survey (GSS) has been collecting demographic, behavioral and attitudinal information since 1972 to monitor changes within the US and to compare the US to other nations. Support for capital punishment (the death penalty) in the US is shown in 1974 and in 2006 in the following table.
Year Favor Oppose Total
1974 937 2006 1945 Total 2882
473 1410
870 2815 1343 4225
(a) (4 points) Find a 95% confidence interval for the change in the proportion supporting capital punishment between 1974 and 2006.
(b) (7 points) Use an ¦Á level of 0.05 to test if the proportion supporting capital punishment has not changed.
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