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Statistics Final Exam: Analyzing Alcohol Consumption and Age, Slides of Data Communication Systems and Computer Networks

Cornell CollegeData Communication Systems and Computer Networks

chats, text messaging, or any form of communication with another human being ... The first two questions involve analyzing data from your fellow students.

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2022/2023

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Final Exam
Stats 120A
Winter 2005
Name:
Instructions:
This final is due Wednesday, March 23rd, 4pm. You may ask me any question you like,
but you may not talk to anyone else about the exam. This includes emails, internet
"chats", text messaging, or any form of communication with another human being. You
are welcome, though, to make use of the UCLA library and its electronic archives. You
are welcome to use any books or any notes from class. And you are welcome to ask me
any question you like.
I will accept hardcopies only. No emailed exams. If you can't turn it in hardcopy form
by March 23, then you need to turn it in earlier.
The first question is worth 20% each. The last is worth 80%.
The first two questions involve analyzing data from your fellow students. The directions
are rather vague: "Analyze". This means you should provide:
1) The URL of the file.
Only the last two items in the pathname are unique, and you need
only supply these. For example, do not write
"http://www.stat.ucla.edu/~rgould/120w05/dataproject/smiith/experiment.t
xt" Instead write "smiith/experiment.txt".
2) The "research question" you will answer. This is a question about the
real world and not about statistics. So "What is the value of the slope
between height and weight?" is NOT a valid research question. But "To
what extent are height and weight related?" is a valid question.
3) Your answer to the research question.
4) A short description of how you analyzed the data to achieve this
answer, along with a clear statement of any assumptions you made.
5) A discussion of why you think those assumptions are valid. If you feel
they are not valid, discuss how this affects your conclusion. (Be sure you
chose a research question that can be answered with this data!)
CHOOSE ONE OF PROBLEMS #1 AND #2:
1. Choose a data set from the dataproject directory that is NOT your own and analyze it.
pf3
pf4

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Final Exam

Stats 120A Winter 2005 Name: Instructions: This final is due Wednesday, March 23rd, 4pm. You may ask me any question you like, but you may not talk to anyone else about the exam. This includes emails, internet "chats", text messaging, or any form of communication with another human being. You are welcome, though, to make use of the UCLA library and its electronic archives. You are welcome to use any books or any notes from class. And you are welcome to ask me any question you like. I will accept hardcopies only. No emailed exams. If you can't turn it in hardcopy form by March 23, then you need to turn it in earlier. The first question is worth 20% each. The last is worth 80%. The first two questions involve analyzing data from your fellow students. The directions are rather vague: "Analyze". This means you should provide:

  1. The URL of the file. Only the last two items in the pathname are unique, and you need only supply these. For example, do not write "http://www.stat.ucla.edu/~rgould/120w05/dataproject/smiith/experiment.t xt" Instead write "smiith/experiment.txt".
  2. The "research question" you will answer. This is a question about the real world and not about statistics. So "What is the value of the slope between height and weight?" is NOT a valid research question. But "To what extent are height and weight related?" is a valid question.
  3. Your answer to the research question.
  4. A short description of how you analyzed the data to achieve this answer, along with a clear statement of any assumptions you made.
  5. A discussion of why you think those assumptions are valid. If you feel they are not valid, discuss how this affects your conclusion. (Be sure you chose a research question that can be answered with this data!) CHOOSE ONE OF PROBLEMS #1 AND #2:
  1. Choose a data set from the dataproject directory that is NOT your own and analyze it.
  1. Choose either your own "controlled" or "observational" data set (the one that you submitted) and analyze it. DO PROBLEM #3:
  2. A recent NY Times article ("More Birthdays and Less Alcohol", March 1 2005) announced a UCLA study that confirmed the long-held belief that the amount of alcohol that people drink declines with age. The study was based on a random sample of about 14000 adults in the US who were surveyed at approximately 5 year intervals for 20 years. A small subset of the data is available at http://www.stat.ucla.edu/~rgould/120w05/datasets/alcohol.small.txt This is a text file that is tab-delimited and includes a header. About the data: qfi stands for "quantity/frequency index". Approximately, it is average the number of alcoholic drinks per day the subject has reported drinking, for the last month (at the time of the survey.) There are two such variables. qfi82 was assessed in 1982 and qfi92 was assessed in 1992. Keep in mind that these are the same people -- the first variable is how much they drank in 1982 and the second how much in 1992. The other variables are self- explanatory, except for X, which is simply the row number. A note about log transforms: You might possibly want to take the log of a variable that has negative values. This is impossible, of course, and so there's a little trick. Suppose that x is a vector and x has negative values: smallest.x <- min(x[!is.na(x)]) log.x <- log(x - smallest.x + 1) The basic idea is that we shift the distribution of x over so that the new smallest value is bigger than 0. To do this we need to know the minimum value, and that's what the first line does. (R assumes that the "missing" value is the smallest possible value, and so we have to exclude missing values from our consideration, which is what that "!is.na(x)" is all about. Answer the following questions. a) (2 pts for right choice, 3 pts for good explanation.) At one stage of their investigation, researchers fit a regression line to examine how drinking varies with age. This is their output: Log(qfi92) = -1.455 -0.011*age and here is the R output:

Note: the published study used a 20 years worth of data based on four surveys administered every 5 years. The extract that you have been provided with includes some of the responses from the second and fourth surveys.