7.14 SAT scores. The standard deviation of SAT scores for students at a particular Ivy League college is 250 points. Two statistics students, Raina and Luke, want to estimate the average SAT score of students at this college as part of a class project. They want their margin of error to be no more than 25 points. (a) Raina wants to use a 90% confidence interval. How large a sample should she collect? (b) Luke wants to use a 99% confidence interval. Without calculating the actual sample size, determine whether his sample should be larger or smaller than Raina's, and explain your reasoning. (c) Calculate the minimum required sample size for Luke.

A random sample of 40 12th-grade students was asked how long it took to get to school. The sample mean was 15.5 minutes and the sample standard deviation was 12.7 minutes. a. Find a 95% confidence interval for the population mean time it takes 12th-grade students to get to school. b. Would a 90% confidence interval based on this sample data be wider or narrower than the 95% confidence interval? Explain. Check your answer by constructing a 90% confidence interval and comparing the width of the interval with the width of the 95% confidence interval you found in part (a). a. The 95% confidence interval is from minutes to minutes. (Round to two decimal places as needed. Use ascending order.) b. Would a 90% confidence interval based on this sample be wider or narrower than the 95% confidence interval? O A. The 90% interval is wider because it has a lower confidence level, and therefore uses a smaller critical value, which creates a wider interval. O B. The 90% interval is wider because it…

Thelma and Louise are each attempting to estimate the proportion of adults who enjoy listening to country music. They each survey a different random sample of adults, and in each sample, the proportion who say they enjoy listening to country music is 0.29. Thelma and Louise each use their sample data to construct a confidence interval. Thelma's interval is from 0.242 to 0.338 and Louise's interval is from 0.237 to 0.323. One of these intervals was computed correctly and the other was not. Which interval must be the correct one? It's impossible to answer this question without knowing the level of confidence used for each interval. It's impossible to answer this question without knowing the sample sizes. O It's impossible to answer this question without knowing the sample sizes or the level of confidence used for each interval. Thelma's interval must be the correct interval. O Louise's interval must be the correct interval.

Siblings Mary and David are each attempting to estimate the proportion of families in their neighborhood who have five or more children. Mary selects a random sample of 50 families to survey, and she observes a sample proportion of 0.10. David selects a random sample of 100 families to survey, and he also observes a sample proportion of 0.10. Mary and David each use their sample data to construct a 95% confidence interval. Who will have the more narrow confidence interval? A. Both intervals will have the same width since the sample proportions are the same. B. Both intervals will have the same width since the level of confidence is the same for each interval. C. Both intervals will have the same width since the sample proportions are the same and the level of confidence is the same for each interval. D. Mary's interval will be more narrow than David's interval. E. David's interval will be more narrow than Mary's interval.