CIS 343 - T 1 A 95 confidence interval is wider than a 90...

Info icon This preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
T 1. A 95% confidence interval is wider than a 90% confidence interval. F 2. A poll cannot have both selection bias and non response bias at the same time. T 1. A confidence interval will always include X F 2. Exclusion bias occurs when some questions in a survey are not answered and therefore the answer is excluded. F 3. The Central Limit Theorem says that the probability that X is closer to . F 1. A data point that is 2 SD’s away from the center is a typical data point. T 3. Response bias is when the response to a question is given incorrectly. T 1. A point estimate X can be far from the true value . F 2. The wider a confidence interval is the less confidence you have in it. F 3. Selection bias happens when the people selected to be polled refuse to answer selected questions in the survey. 4. On the normal curve Find the area a) between -1.25 and 0. Ans. = .5 - .1056 = .3944 b) between -.70 and 1.21 Ans. = .8869 - .2420 = .6449 Find z if the area c) to the left of z is .0764 Ans. z=-1.43, small area to left means z is negative, finding .0764 in the body of the z table gives z=-1.43 d) to the left of z is .9394 Ans. z=1.55, large area to left means z is positive, finding .9394 in the body of the z table gives z=1.55 6. Jake wants to learn Spanish on his own and every week studies either 2, 6, or 7 hours at random. His SD for studying Spanish is 2.16 hours per week. In one year find a range for the total number of hours he will spend on learning Spanish. This is a gambling problem in disguise. The box has three tickets 2,6,7 so the average of the box is μ=5, σ=2.16. Total hours for the year is the sum of each week. Expected(winnings)=nμ=52*5=260 SD(winnings)=√n*σ=√(52)*2.16=15.576 Rough range is 260±15.576 or 244.424 to 275.576 9. The President of Murray State wants a confidence interval for the average number of students who go to summer school at MSU. A sample of 8 summers yielded an average of 900 students with a standard deviation of 200 students. Find an 80% confidence interval. This is a t-confidenceinterval since the SD is connected to the sample size n. X ±t*s/√n With .8 in the middle gives .1 in the right tail and with 8-1=7df gives t=1.415 CI is 900±1.415*200/√8 CI is 900±100.06 or 799.94 to 1000.06
Image of page 1

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

View Full Document Right Arrow Icon
9. a) Interpret the CI in words. We believe the true average number of students in summer school is between 799.94 and 1000.06 with 80% confidence. 9. b) Do you believe the true average could be as high as 1050 students? Explain. 1050 is outside the interval and would be considered too high for the true ave. 10. A psychologist says that looking at sunsets is good for your mental health. The psychologist wants to see now whether people in Kentucky or Missouri spend more time watching sunsets. The SD for watching sunsets in Kentucky is 3 hours per month per person, and in Missouri it is 2 hours per month per person. Since the SD is one and a half times bigger in Kentucky, he will sample one and a half as many people in Kentucky compared to Missouri. The sample size in Kentucky is 150 people and the sample size in Missouri is 100 people. The psychologist believes that the accuracy in the two states will be the same, do you agree? Explain.
Image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the 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