Stat104_studyguide_part1_SOLUTIONSv34

Stat104_studyguide_part1_SOLUTIONSv34 - Stat 104 :...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon
Study Guide Solutions, Part 1 Stat 104 : Quantitative Methods for Economists
Background image of page 1

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

View Full DocumentRight Arrow Icon
Practice Problems 1) Describe the shape of the histogram: This histogram is bimodal; that means it has two distinctive peaks. It also might be called skewed to the right. 2) For the histogram pictured below, what proportion of the terms are less than 3.5? There are 25 items total, 11 of which are less than 3.5. So the answer is 11/25.
Background image of page 2
3) You want to do a survey of members of the senior class at your school and want to select a simple random sample. You intend to include 40 students in your sample. Which of the following approaches will generate a simple random sample? (a) Write the name of each student in the senior class on a slip of paper and put the papers in a container. Then randomly select 40 slips of paper from the container. (b) Assuming that students are randomly assigned to classes, select two classes at random and include those students in your sample. (c) From a list of all seniors, select one of the first 10 names at random. Then select every nth name on the list until you have 40 people selected. (d) Select the first 40 seniors to pass through the cafeteria door at lunch. (e) Randomly select 10 students from each of the four senior calculus classes. The answer is (a). In order for this to be a simple random sample, all samples of size 40 must be equally likely. None of the other choices do this [and choice (d) isn’t even random]. 4) Interviewers, after the 9/11 attacks, asked a group of Arab Americans if they trust the administration to make efforts to counter anti-Arab activities. If the interviewer was of Arab descent, 42% responded “yes” and if the interviewer was of non-Arab descent, 55% responded “yes.” What seems to be going on here? Almost certainly, respondents are responding in a way they feel will please the interviewer. This is a form of response bias—in this circumstance, people may just not give a truthful answer. 5) A shopping mall wants to know about the attitudes of all shoppers who visit the mall. On a Wednesday morning, the mall places 10 interviewers at a variety of places in the mall and asks questions of shoppers as they pass by. Comment on any bias that might be inherent with this approach. The study suffers from undercoverage of the population of interest, which was declared to be all shoppers at the mall. By restricting their interview time to a Wednesday morning, they effectively exclude most people who work. They essentially have a sample of the opinions of nonworking shoppers. There may be other problems with randomness, but without more specific information about how they gathered their sample, talking about it would only be speculation.
Background image of page 3

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

View Full DocumentRight Arrow Icon
6) If you are told that a data set has a sample mean of 25 and a sample variance of 0, you can conclude that: a. the data set is {-25,25} b. there are no observations in the data set c. all of the observations in the data set are 25 d. someone has made a mistake e. none of the above 7)
Background image of page 4
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 03/27/2012 for the course STATS 104 taught by Professor Michaelparzen during the Fall '11 term at Harvard.

Page1 / 50

Stat104_studyguide_part1_SOLUTIONSv34 - Stat 104 :...

This preview shows document pages 1 - 5. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online