MATH 1070-070: Quiz 2
May 29, 2008
Name:
No outside materials are allowed except pens, pencils, erasers, and calculators. You have one
half hour to complete this quiz. Please keep nervous ticks to a minimal so as to not disrupt
anyone else taking the quiz. Anyone caught cheating will be punished with a grade of 0%.
You may need the following:
1 X
1 X
r=
Zx Zy =
n−1
n−1
x − x̄
Sx
ŷ = a + bx
Sy
b=r
a = ȳ − bx̄
Sx
1
y − ȳ
Sy
1. (40 points; 5 each) Here are the data of average time spent reading per day per person and the rates
of death from Alzheimers disease for 5 unnamed countries.
x = reading time (in minutes):
26 30 34 27 15
y = Alzh. rate (in # deaths per 100,000 people): 1.9 1.7 1.5 1.7 2.3
We would like to know whether the rate of death from Alzheimers can be predicted from the average
reading time.
(a) Using your calculator statistics functions, find the mean reading time, the mean Alzheimers death
rates, and find the standard deviation of both reading times and death rates for this data set.
(b) Find the correlation, r, between reading times and death rates. Hint: You’ll need to find the
z-scores first.
(c) Does the r value that you obtained, indicate positive association, negative association or no linear
association between these variables?
(d) Make a scatterplot.
(e) Find the regression equation for the data, ŷ.
(f) Plot the regression line on the same graph as the scatterplot.
(g) Looking at the graph and the r value, do you think the following statement is justified: Lack of
reading causes high rates of death from Alzheimers?
(h) Based on your results, what Alzheimers death rate would you predict for a country with average
reading time 20 minutes per day per person?
2
This page is left intentionally blank for scratch work.
3
2. (20 points) A middle school has 350 students in its’ graduating class. Start with the second row of
digits in the random number table to select a simple random sample of ten students.
If the students are numbered 001 to 350, what are the numbers of the ten students selected?
4