4. Find the critical value (or values) of the t-test for each.

a.n = 15, a = 0.05, right-tailed

b.n = 23, a = 0.005, left-tailed

c.n = 28, a = 0.01, two-tailed

d.n = 17, a = 0.02, two-tailed

8. Cost of Braces The average cost for teeth straightening with metal braces is approximately S5400.A nationwide franchise thinks that its cost is below that figure.A random sample of 28 patients across the country had an average cost of $ 5250 with a standard deviation of $ 629.At a = 0.025, can it be concluded that the mean is less than $ 5400?

10. Number of Words in a Novel The National Novel Writing Association states that the average novel is at least 50k words .A particularly ambitious writing club at a college-preparatory high school had randomly selected members with works of the following lengths.At a = 0.10, is there sufficient evidence to conclude that the mean length is greater than 50k words?48,972 50, 100 51,560 49,800 50,020 49,900 52,193 i B

12. Chocolate Chip Cookie Calories The average 1-ounce chocolate chip cookie contains 110 calories.A random sample of 15 different brands of 1-ounce chocolate chip cookies resulted in the following calorie amounts.At the a = 0.01 level, is there sufficient evidence that the average calorie content is greater than 110 calories?100 125 150 160 185 125 155 145 160 100 150 140 135 120 110 Source: The Doctor's Pocket Calorie, Fat, and Carbokydrate Counter.

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6. StoCKs and MUlual Fund Ownersmip it has Deen found that 50.5% of U.S.households own stocks and mutual funds.A random sample of 300 heads of households indicated that 171 owned some type of stock.At what level of significance would you conclude that this was a significant difference?

8. Female Physicians The percentage of physicians who are women is 27.9%.In a survey of physicians employed by a large university health system, 45 of 120 randomly selected physicians were women.Is there sufficient scientific evidence at the 0.05 level of significance to conclude that the proportion of women physicians at the university health system exceeds 27.9%?

10. Undergraduate Enrollment It has been found that 85.6% of all enrolled college and university students in the United States are undergraduates.A random sample of 500 enrolled college students in a particular state revealed that 420 of them were undergraduates.Is there sufficient evidence to conclude that the proportion differs from the national percentage?Use a = 0.05.Source: Time Almanac.