Download Research Statistics: Homework 6 Solutions - Confidence Intervals & Hypothesis Testing and more Assignments Statistics in PDF only on Docsity! Basic Statistics for Research (01:960:401:02) Fall 2004 Homework 6 Chapter 19: 1, 2, 3, 4, 5, 6, 7, 8, 12, 15, 18, 31 Chapter 20: 1, 2, 4, 8, 11, 19, 22, 23 Here are the solutions to the even numbered problems. Chapter 19: 2. He believes the true proportion is within 3% of his estimate , with some (probably 95%) degree of confidence. That is to say, ± 3% gives us an interval that covers the true proportion with probability 95% (the degree of the confidence interval). About 5% of the 95% confidence intervals he finds fail to cover the true proportion. p̂ p̂ 4. a) Population -- people who recently bought new cars; Sample -- 167 people surveyed; p -- proportion of all new car buyers who are dissatisfied with the salesperson; -- proportion of those surveyed who are unsatisfied (3%); p̂ Can't use methods of this chapter because only 5 people were dissatisfied. b) Population -- college students; Sample -- 2883 students who were asked about cell phones; p -- proportion of college students with cell phones; -- proportion of those asked who have cell phones (8.4%); p̂ Use methods of this chapter with caution -- students entering the football stadium may not reflect all students. c) Population -- potato plants in the United States; Sample -- 240 plants checked; p -- proportion of all plants in the field with blight; -- proportion of the 240 plants checked with blight (2.9%); p̂ Can't use methods of this chapter -- fewer than 10 "successes". d) Population -- employees at the company; Sample -- all employees that year; p -- proportion of all employees who will have an injury on the job in a year; -- proportion of that year's employees with an injury (3.9%); p̂ Can use methods of this chapter if that year's employees are viewed as a random sample of all possible employees. 6. a) Not correct. The interval is about the proportion of heads, not individual coins. b) Not correct. We know in this sample that 56% of the spins were heads. c) Not correct. The interval is about the proportion of heads, not about individual spins. d) Not correct. The interval is about the proportion of heads, not about individual spins. e) Not correct. The interval is about the proportion of heads, not about the percentage of euros. 8. a) True. b) True. c) True. d) True.
