Q1. Acid rain has caused many lakes to become more acidic. A lake is considered nonacidic if the PH level is greater than 6. The PH level for 15 lakes was:
7.2, 7.3, 6.1, 6.9, 6.6, 7.3, 6.3, 5.5, 6.3, 6.5, 5.7, 6.9, 6.7, 7.9, and 5.8
At "alpha" = 0.05, is there enough evidence to conclude that, on average, these lakes are nonacidic?
Q2. A used car salesman claims that the average price of a 2009 Honda Accord LX is $20,500. You, of course, distrust him (you feel that it is much lower) and find that a random sample of 14 similar cars has a mean of price of $19,850 with a standard deviation of $1084. Is there enough evidence to reject the salesman's claim at "alpha" = 0.05?
Q3. Some big shot Institute claims that 25% of college graduates believe that a college degree is not worth the cost. To test this hypothesis you ask a random sample of 200 graduates and 21% agree with that a degree is not worth the cost. At "alpha" = 0.10, is there enough evidence to reject the claim?
Q4. A 2009 national poll of 1053 U.S. adults found that 548 favored the Governments plan for a stimulus package of a minimum of 800 billion dollars Using "alpha" = 0.05, do the data provide evidence to conclude that a majority (more than 50%) of adults favored passage?
Q5. A sporting goods producer claims that the variance of the strengths of a certain fishing line is 15.9. A random sample of 15 spools has a variance of 21.8. At "alpha" = 0.01, can the claim be proven wrong? Assume the population is normally distributed.
Q6. The standard deviation of the amount of fat in whole milk is claimed to be no greater than 0.50 by the Dairy Association. You do not believe this. You find that a random sample of 31 milk containers has a standard deviation of 0.53. Using "alpha" = 0.05, is there enough evidence to reject the Association's claim? Would your conclusion change if "alpha" = 0.01? Assume the population is normally distributed.
Q7. A national faculty group conducts salary surveys each year. For 2008, 35 University Professor's had an average salary of $88,200 and 30 Community College Instructor's had an average salary of $73,200. The population standard deviations are known to be $25,800 and $25,600, respectively. At "alpha" = 0.01, can we conclude that university salaries are higher than at the CC's?
Q8. A USA Today Snapshot states that the government claims that there is a significant difference in the mean credit card debts of households in New York and Texas. A sample of 250 households from each state gave these results: NY mean = $4446.25 with deviation = $845.70 while for TX the mean = $4567.24 with deviation = $561.95. At "alpha" = 0.10, is there a significant difference in debt? Part two: would your conclusion change if "alpha" were .05?
Q9. The average AIMS test scores for two different teachers in Cochise County were 473 (8 students) and 459 (18 students.) The respective deviations were 39.7 and 24.5. Can it be concluded that the averages are different at Alpha = 0.10?
Q10. Find the 90% confidence interval for problem #9 above.