Unit 9: Surveys: Percentages and Averages
Text reading and homework:
Read chapters 20, 21 and 23 of FPP and do the following
Chapter 20 (pages 371-373): 1, 3, 4, 5, 6
Chapter 21 (pages 391-394): 1, 2, 3, 4, 11
Chapter 23 (pages 425-428): 1, 2, 3, 4, 5
"Pollster discusses McCain, Obama and the problems with polls,"
by Jeremy Duda, November 7, 2008, Arizona Capitol Times
LexisNexis Academic(make sure to select the "News" tab instead of "General")
Possible Essay Questions:
- What type of error does the official "statistical error" reported
with most polls refer to? If the polls are "subject to statistical error
of 2-3 percentage points", how can two polls differ by more than 6 points?
What kind of problems does the article identify are made by
typical election polls?
- How can we achieve the same margin-of-error by sampling
400 people, regardless of the population size?
How can polls be used to influence subsequent polls, or the
election for that matter?
- Use a spreadsheet to carry out 30 simulations of the two
strategies (i) and (ii) discussed in Problem 9 of Chapter 17 (page 305).
How do your simulation results compare with your theoretical answers
for 9a), b) and c)? Explain.
- A multiple-choice quiz has 25 questions. Each question has 5
possible answers, only one of which is correct. Four points are given
for each correct answer, but a point is taken off for a wrong
answer. Use a spreadsheet to simulate the scores of 100 students
answering all of the questions at random. How many, and what
percentage, of the students score at least 10 points? Compare your
results with those obtained by theoretical computation using
expected value and standard error. Repeat the simulation and
comparison with 400 simulated students guessing randomly.
Use each column of the spreadsheet as a single simulation of 1000 plays.
The number in each cell should contain the winnings on one spin of the
roulette wheel. [i.e. for 9(i) -- the columns strategy -- the contents
of a cell might be
Below each simulation, calculate the total winnings.
To count how many of the simulations "came out ahead", won 100 or
lost 100, use the FREQUENCY function with the "data array" being the
row of total winnings, and the "bin array" being -100,0,100 (put
these numbers in three adjoining cells.) The function FREQUENCY
counts how many times an outcome was less than each bin label: So,
the number next to -100 is the number of times we lost more than $100.
The number next to 0 is the count between -$100 and $0. The number
next to $100 is the count between $0 and $100 and the last number is
the count greater than $100. (Note: four counts for three bin numbers.)