Problems
1. Suppose the historical average work week was 39.2 hours and SD was 4.8 hours as reported by the labor Dept. This year a study of 112 workers showed a mean of 38.5 hours. Test whether the workweek is the same or significantly shorter due to the recession. (Left tail). Use a .10 significance level.
a. Calculate the appropriate Z or T —————————–
b. What is the appropriate Critical value T or Z ——————————–
c. Statistical conclusion —————————————————-
d. Practical conclusion —————————————————————
2. A Shell oil company executive says (Claims) that a majority of workers – more than 50% – prefer a 10 hour four day work week over an 8 hour five day work week. Of a 105 worker sample, 67 said they prefer a 10-hour-4-day work-week. At alpha- significance level of 0.10 does this sample support the executive’s suggestion (more than 50%, right tail)
e. Critical Value
f. What is the appropriate calculated test statistic T or Z
g. Statistical conclusion. Practical conclusion
3. The financial industry Earnings average per share last year were $3. This year, earnings per share in 10 financial companies were as follows. Test the hypothesis that this year’s earnings differ (higher or lower) from last year – two tail, at alpha (significance level) =.01
Data 1.92, 2.16, 3.63, 3.16, 4.10, 3.14, 2.20, 2.34, 3.10, 2.38
Hypothesis being tested : Mean=3
h. Critical Value T or Z
i. What is the appropriate
j. Statistical conclusion
k. Practical conclusion
4. A study showed that 110 of 200 people say that their major source of news is TV.
l. What would be a 99% confidence interval for the proportion?
m. What i s the appropriate sample size if you want to re-conduct that survey
5. Confidence Interval : A sample of 100 CNN viewers shows an average household income of 119 K and a standard deviation of 30k.
n. What would the 99% confidence interval of the mean be? ___________
o. What is an appropriate sample size?
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