# UW STAT 220 - Exam Guide (10 pages)

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## Exam Guide

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- Pages:
- 10
- School:
- University of Washington
- Course:
- Stat 220 - Basic Statistics

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Stat220 Final exam version A Dec 12 2006 Name print Section This is the final exam for Stat220 There are 7 questions for a total of 59 points You have until 10 15am to work on the exam A normal table is provided on the last page and you can use the back side of that page as scratch paper Exam rules 1 You must keep the exam closed and are not allowed to write until it is announced that you can start the exam 2 This is a closed book exam but you can use one page of notes letter sized double sided 3 You may use a calculator Cell phones may not be used 4 Just like in the homeworks you won t get points for an answer without explanation So make sure to show your work and explain all your answers 5 Write your name and section on the exam and sign the honor statement below certifying that the exam is completely your own work 6 Code of conduct you must do this exam completely independently Students suspected of cheating or dishonest practices will be reported to the Vice President of Student Affairs Such practices include but are not limited to i making use of books or material other than your page of notes ii communicating with other students in any way iii looking at the work of other students and iv purposely exposing your work to the view of other students 7 At 10 15 it will be announced that everybody must stop writing and close the exam You must stay seated and no talking is allowed The exams will be collected row by row Once you have submitted your exam you must directly leave the room without talking Good luck Honor statement I certify that this exam is completely my own work and that I followed the code of conduct as outlined in point 6 above Signature Q1 9 pt Q2 7 pt Q3 6 pt Q4 8 pt Q5 7 pt 1 of 10 Q6 8 pt Q7 14 pt Total 59pt Stat220 Final exam version A Dec 12 2006 1 This question contains four independent parts 3 a In the U S in 1990 20 273 people were murdered compared to 16 848 in 1970 nearly a 20 increase Do these numbers show that the US became a more violent society over the period 1970 1990 Explain your answer 3 b A nationwide telephone survey about homelessness used random digit dialing Out of 1 507 respondents 3 said they had been homeless at some point in the last five years Is there selection bias in this 3 estimate If so would you guess the real percentage to be higher or lower Explain your answers 2 of 10 Stat220 3 Final exam version A Dec 12 2006 c The table below shows the batting averages of two baseball players for the first half of the season for the second half of the season and for the total season Note that player A had a better batting average for the first half of the season and also for the second half of the season but a lower batting average for the total season Is this possible or must we have made an error somewhere If you think it is possible explain what kind of statistical phenomenon this is and how this example fits in If you think it is not possible explain why Player A Player B First half of season 0 40 0 35 Second half of season 0 25 0 20 3 of 10 Total season 0 264 0 336 Stat220 Final exam version A Dec 12 2006 2 The following data set is given x y 4 4 4 2 3 1 3 5 1 5 3 7 Moreover it is given that Average of x 3 Average of y 4 SD of y 2 3 a Compute the SD of x Show your work you can expand the table above 4 b Compute the correlation coefficient r Show your work you can expand the table above 4 of 10 Stat220 Final exam version A Dec 12 2006 3 For women age 25 29 in Seattle in 1970 the relationship between income and education can be summarized as follows Education Income r 0 3 Average 12 years SD 3 1 years Average 11 600 SD 10 500 3 a Predict the income of a woman with 14 years of education 3 b Fill in the blank This prediction is likely to be off by or so Or can t this be determined from the given information Explain your answer 5 of 10 Stat220 Final exam version A Dec 12 2006 8 4 Pearson and Lee obtained the following results in a study of about 1 000 families height of husband average 68 inches SD 2 7 inches height of wife average 63 inches SD 2 5 inches r 0 23 The scatter diagram is football shaped Among the couples with husbands who were about 65 inches tall what percentage of the wives were taller than their husbands Show your work 6 of 10 Stat220 Final exam version A Dec 12 2006 5 This question contains two independent parts 4 a In a study of Danish draftees T W Teasdale and associates found a positive correlation between near sightedness and intelligence Indicate which of the following are true and which are false Explain your answer i Draftees who were more near sighted were also more intelligent on the average ii Draftees who were more intelligent were also more near sighted on the average iii The data show that near sightedness causes intelligence iv The data show that intelligence causes near sightedness 3 b One hospital has 218 live births during the month of January Another has 536 Which is likelier to have 55 or more male births Or is it equally likely Explain There is about a 52 chance for a live born infant to be male 7 of 10 Stat220 Final exam version A Dec 12 2006 6 A candy cane factory has a large collection of candy canes Their average weight is 1 0 ounce and their SD is 0 03 ounces A machine takes a simple random sample of 1000 candy canes 4 a Fill in the blanks the 1000 candy canes weigh about ounces give or take or so Explain your answer by relating the problem to a box model 4 b Estimate the chance that the 1000 candy canes weigh more than 1002 ounces If you use the normal approximation explain why that is justified 8 of 10 Stat220 Final exam version A Dec 12 2006 7 This question is about the percentage of people who are living in poverty in major US cities 4 a We take a simple random sample of 2 200 people in Tacoma It turns out that 13 of the people in the sample are living in poverty Compute a 95 confidence interval for the percentage of people in Tacoma who live in poverty and give a precise interpretation of your confidence interval 3 b The national percentage of people who are living …

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