HonorsExam2 - STA 2023 Honors Name Fall 2009 Exam 2 UF ID A...

Info icon This preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
Image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: STA 2023 Honors Name Fall 2009 Exam 2 UF ID# A 1- FORMULAS : Binomial Porportion p : mean = p stdev = M n — 0' Sample Mean X : mean = u stdev = T n 1. As part of a statistics class project, a group of students stationed themselves outside of Hume Hall on a Tuesday night. They asked 60 students entering and leaving the dorm how many text messages they had sent the previous day. The mean was 23.25 and the standard deviation 33.4. a) Let X be the number of text messages sent by each person. What can you say about the distribution of X? Explain. (5 pts) b) Let A7 be the average number of text messages for the sample. What can you say about the distribution of X ? Explain. (5 pts) 0) Construct a 95% confidence interval for u. (8 pts) d) Interpret the confidence interval, paying special attention to the assumptions, and the population the conclusions should be extended to. (5 pts) _____________J 2. Another group project wanted to estimate the proportion of “stoners” at UF. They asked the question: “In the past year, on average, did you smoke marijuana 3 or more times per month?” 52 out of 76 people answered yes. a) State the assumptions necessary for the validity of the confidence interval. Are they satisfied? Explain. (5 pts) b) Construct a 96% confidence interval for p and interpret. (12 pts) 3. If you wanted to estimate the proportion of “stoners” at UF to within 5% of the truth, with 95% confidence, how large a sample should you take? (6 pts) 4. 5. A recent study considered whether daily consumption of 1200mg of garlic could reduce tick bites. The study used a crossover design with a sample of Swedish military conscripts, half of whom used placebo first and garlic second, and half the reverse. Garlic was more effective for 37 of the subjects, and the placebo for 29 of them. Conduct the significance test to determine if the study suggests a real benefit to using garlic, or if the results consistent with random variation. Make sure you include all the steps, clearly marked, and your conclusions. (18 pts) True/False: 95% confidence interval for the average amount of time students spend on Facebook each day: (1.3, 2.1). (10 pts) 95% of students spend between 1.3 and 2.1 hours on F acebook each day. Most students spend between 1.3 and 2.1 hours on F acebook each day. We are 100% confident that the average amount of time spent on F acebook each day by students in the sample is more than one hour. We are 95% confident that the average amount of time spent on Facebook each day by students in the population is more than one hour. Even if the sample is not truly random and representative of the population, the confidence interval is still valid. 6. 7. 8. Experts determined that, because of the economy, 88% of American households were planning to cut back on their Halloween spending this year. We will select a random sample of 500 American households and ask them if they cutback this year. a) Let X be the number of people in the sample that answer “yes”. What is the distribution of X? Explain. (5 pts) b) Let f) be the proportion of people in the sample that answer “yes”. What is the distribution of f) ? Explain. (5 pts) c) Find the probability that more than 85% in the sample answer “yes”. (6 pts) Briefly describe what the distribution of 1? would look like if we had: (3 pts) a) Normal population, n=5 b) Skewed right population, n=15 c) Uniform population, n=50 Briefly explain when and why we use the t distribution. (2 pts) ...
View Full Document

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern