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University of Saskatchewan *

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245

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Economics

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Jan 9, 2024

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1. A random sample of n = 49 observations has a mean x = 26.3 and a standard deviation s = 3.4. (a) Give the point estimate of the population mean . ? Find the 95% margin of error for your estimate. (Round your answer to four decimal places.) (b) Find a 90% confidence interval for . (Round your answers to three decimal ? places.) ___ to ___ What does "90% confident" mean? In repeated sampling, 10% of all intervals constructed in this manner will ? enclose the population mean. There is a 10% chance that an individual sample mean will fall within the ? interval limits. There is a 90% chance that an individual sample mean will fall within the ? interval. 90% of all values will fall within the interval limits. ? In repeated sampling, 90% of all intervals constructed in this manner will ? enclose the population mean. (c) Find a 90% lower confidence bound for the population mean . (Round your answer ? to two decimal places.) Why is this bound different from the lower confidence limit in part (b)? This bound is calculated using , while the lower confidence limit in part (b) ? z? is calculated using /2. z? This bound is calculated using sqrt(n), while the lower confidence limit in ? part (b) is calculated using n. This bound is calculated using /2, while the lower confidence limit in part ? z? (b) is calculated using . z? The lower bounds are based on different values of x. ? This bound is calculated using n, while the lower confidence limit in part (b) ? is calculated using sqrt(n). (d) How many observations do you need to estimate to within 0.5, with probability ? equal to 0.95? (Round your answer up to the nearest whole number.) 2. A random sample of n = 500 observations from a binomial population produced x = 110 successes. (a) Find a point estimate for p. Find the 95% margin of error for your estimator. (Round your answer to three decimal places.) (b) Find a 90% confidence interval for p. (Round your answers to three decimal places.) Interpret this interval. In repeated sampling, 90% of all intervals constructed in this manner will ? enclose the population proportion. There is a 90% chance that an individual sample proportion will fall within the ? interval. There is a 10% chance that an individual sample proportion will fall within the ? interval. In repeated sampling, 10% of all intervals constructed in this manner will ? enclose the population proportion. 90% of all values will fall within the interval. ?
3. Independent random samples were selected from binomial populations 1 and 2. Suppose you wish to estimate (p1 − p2) correct to within 0.02, with probability equal to 0.99, and you plan to use equal sample sizes—that is, n1 = n2. How large should n1 and n2 be? (Assume maximum variation. Round your answer up to the nearest whole number.) n1 = n2 = 4. Acid rain, caused by the reaction of certain air pollutants with rainwater, is a growing problem in the United States. Pure rain falling through clean air registers a pH value of 5.7 (pH is a measure of acidity: 0 is acid; 14 is alkaline). A sample of n = 50 rainfalls produced pH readings with x = 3.6 and s = 0.6. Do the data provide sufficient evidence to indicate that the mean pH for rainfalls is more acidic (Ha: < 5.7 pH) than pure rainwater? Test using = 0.05. Note that this ? ? inference is appropriate only for the area in which the rainwater specimens were collected. State the null and alternative hypotheses. H0: = 5.7 versus Ha: > 5.7 ? ? ? H0: > 5.7 versus Ha: < 5.7 ? ? ? H0: < 5.7 versus Ha: = 5.7 ? ? ? H0: ≠ 5.7 versus Ha: < 5.7 ? ? ? H0: = 5.7 versus Ha: < 5.7 ? ? ? Find the test statistic and rejection region. (Round your answers to two decimal places. If the test is one-tailed, enter NONE for the unused region.) test statistic z = rejection region z > z < State your conclusion. H0 is rejected. There is sufficient evidence to indicate that the average pH ? for rainfalls is more acidic than pure rainwater. H0 is not rejected. There is sufficient evidence to indicate that the average ? pH for rainfalls is more acidic than pure rainwater. H0 is rejected. There is insufficient evidence to indicate that the average pH ? for rainfalls is more acidic than pure rainwater. H0 is not rejected. There is insufficient evidence to indicate that the average ? pH for rainfalls is more acidic than pure rainwater. 5. In a study to assess various effects of using a female model in automobile advertising, 100 men were shown photographs of two automobiles matched for price, colour, and size, but of different makes. One of the automobiles was shown with a female model to n1 = 50 of the men (group A), and both automobiles were shown without the model to the other n2 = 50 men (group B). In group A, the automobile shown with the model was judged as more expensive by x1 = 35 men; in group B, the same automobile was judged as the more expensive by x2 = 26 men. Do these results indicate that using a female model increases the perceived cost of an automobile? Use a one-tailed test with = 0.05. (Round your answers to two decimal places.) ? (1-2) Null and alternative hypotheses: H0: (p1 − p2) ≠ 0 versus Ha: (p1 − p2) = 0 ? H0: (p1 − p2) = 0 versus Ha: (p1 − p2) ≠ 0 ? H0: (p1 − p2) = 0 versus Ha: (p1 − p2) < 0 ? H0: (p1 − p2) = 0 versus Ha: (p1 − p2) > 0 ? H0: (p1 − p2) < 0 versus Ha: (p1 − p2) > 0 ? (3) Test statistic: z =
(4) Rejection region: If the test is one-tailed, enter NONE for the unused region. z > z < (5) Conclusion: H0 is rejected. There is insufficient evidence to indicate that using a female ? model increases the perceived cost of an automobile. H0 is not rejected. There is insufficient evidence to indicate that using a ? female model increases the perceived cost of an automobile. H0 is not rejected. There is sufficient evidence to indicate that using a ? female model increases the perceived cost of an automobile. H0 is rejected. There is sufficient evidence to indicate that using a female ? model increases the perceived cost of an automobile. 6. A random sample of n = 15 observations from a normal population produced x = 47.9 and s2 = 4.4. Test the hypothesis H0: = 48 against Ha: ≠ 48 at the 5% level ? ? of significance. State the test statistic. (Round your answer to three decimal places.) t = State the rejection region. (If the test is one-tailed, enter NONE for the unused region. Round your answers to three decimal places.) t > t < State the conclusion. H0 is rejected. There is sufficient evidence to conclude that the mean ? different from 48. H0 is not rejected. There is sufficient evidence to conclude that the mean is ? different from 48. H0 is not rejected. There is insufficient evidence to conclude that the mean is ? different from 48. H0 is rejected. There is insufficient evidence to conclude that the mean is ? different from 48. 7. To test the effect of alcohol in increasing the reaction time to respond to a given stimulus, the reaction times of seven people were measured. After consuming 89 mL of 40% alcohol, the reaction time for each of the seven people was measured again. Do the following data indicate that the mean reaction time after consuming alcohol was greater than the mean reaction time before consuming alcohol? Use = ? 0.05. (Use before − after = d. Round your answers to three decimal places.) ? ? ? Table: Person | 1 | 2 | 3 | 4 | 5 | 6 | 7 Before | 3 | 5 | 4 | 3 | 2 | 6 | 2 After | 7 | 8 | 2 | 5 | 3 | 5 | 4 (1-2) Null and alternative hypotheses: H0: d = 0 versus d ≠ 0 ? ? ? H0: d = 0 versus d > 0 ? ? ? H0: d ≠ 0 versus d = 0 ? ? ? H0: d < 0 versus d > 0 ? ? ? H0: d = 0 versus d < 0 ? ? ? (3) Test statistic: t = (4) Rejection region: If the test is one-tailed, enter NONE for the unused region.
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t > t < (5) Conclusion: H0 is not rejected. There is sufficient evidence to indicate that the mean ? reaction time is greater after consuming alcohol. H0 is rejected. There is insufficient evidence to indicate that the mean ? reaction time is greater after consuming alcohol. H0 is not rejected. There is insufficient evidence to indicate that the mean ? reaction time is greater after consuming alcohol. H0 is rejected. There is sufficient evidence to indicate that the mean reaction ? time is greater after consuming alcohol. 8. At a time when energy conservation is so important, some scientists think closer scrutiny should be given to the cost (in energy) of producing various forms of food. Suppose you wish to compare the mean amount of oil required to produce 4047 square metres of corn versus 4047 m^2 of cauliflower. The readings (in barrels of oil per 4047 m^2), based on 80,937 m^2 plots, seven for each crop, are shown in the table. Corn Cauliflower 5.5 15.7 7.0 13.6 4.6 17.8 6.0 16.7 7.8 15.9 4.6 16.5 5.9 17.2 Use these data to find a 90% confidence interval for the difference between the mean amounts of oil required to produce these two crops. (Round your answers to three decimal places.) ___ to ___ barrels of oil per square metre