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Chapter 10: Q.132 (page 610)
A new SAT study course is tested on individuals. Pre-course and post-course scores are recorded. Of interest is the mean increase in SAT scores. The following data are collected:
The given data is an independent group means, population standard deviations and/or variances known.
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At Rachel’s 11th birthday party, eight girls were timed to see how long (in seconds) they could hold their breath in a
relaxed position. After a two-minute rest, they timed themselves while jumping. The girls thought that the mean difference
between their jumping and relaxed times would be zero. Test their hypothesis.
Use the following information to answer next five exercises. A study was conducted to test the effectiveness of a juggling class. Before the class started, six subjects juggled as many balls as they could at once. After the class, the same six subjects juggled as many balls as they could. The differences in the number of balls are calculated. The differences have a normal distribution. Test at the significance level
What is the sample mean difference?
Use the following information to answer the next 12 exercises: The U.S. Center for Disease Control reports that the mean life expectancy was years for whites born in 1900 and 33.0 years for nonwhites. Suppose that you randomly survey death records for people born in 1900 in a certain
county. Of the 124 whites, the mean life span was years with a standard deviation of years. Of the 82 nonwhites, the mean life span was years with a standard deviation of 15.6
years. Conduct a hypothesis test to see if the mean life spans in the county were the same for whites and nonwhites.
Explain why you chose the distribution you did for Exercise 10.24.
Use the following information to answer the next five exercises. Two metal alloys are being considered as material for ball bearings. The mean melting point of the two alloys is to be compared. 15 pieces of each metal are being tested. Both populations have normal distributions. The following table is the result. It is believed that Alloy Zeta has a different melting point.
Is this a right-, left-, or two-tailed test?
Use the following information to answer the next 12 exercises: The U.S. Center for Disease Control reports that the mean life expectancy was 47.6 years for whites born in 1900 and 33.0 years for nonwhites. Suppose that you randomly survey death records for people born in 1900 in a certain county. Of the 124 whites, the mean life span was 45.3 years with a standard deviation of 12.7 years. Of the 82 nonwhites, the mean life span was 34.1 years with a standard deviation of 15.6 years. Conduct a hypothesis test to see if the mean life spans in the county were the same for whites and nonwhites.
Which distribution (normal or Student's t) would you use for this hypothesis test?
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