Class 13: Monogamy
Discussion
An article in the New York
Times reports an HIV infection rate for college students of 2 in 1,000. A 1992
study funded by the National Institute of Allergy and Infectious Diseases
estimates the risk of heterosexual transmission of HIV from a single sexual
encounter as follows:
Maletofemale transmission rate: 
0.0005 


Femaletomale transmission rate: 
0.00005 
(These estimates are for unprotected sex) 

(For the following problems,
you may choose the uninfected student to be of either gender)
If an uninfected student has
a single encounter with a randomly selected student of the opposite sex, what
is the probability that he/she will be infected with HIV?
If an uninfected student has
1 encounter each with 100 randomly selected students of the opposite sex, what
is the probability that he/she will be infected with HIV?
If an uninfected student has
100 encounters with one randomly selected student of the opposite sex, what is
the probability that he/she will be infected with HIV?
How do you explain these
results?
Is the above procedure a
reasonable way to estimate risk? If not, why not? If so, what are the
implications?
Journal Assignment:
Read an article in the news
that involves correlation. A good
way to find one is quickly is to go to the website of your favorite newspaper
or magazine and search for the word ÒcorrelationÓ. If you have trouble finding an article you like, or if you
prefer, you can use the article Risky Business that is posted on Blackboard
under Handouts > Class 9.
For whatever article you
use, comment on the article and include answers to the following questions. If you use your own article,
please include a copy with your journal so that I can read it, too.
1) What variables was the
correlation between (e.g. height and weight, or temperature and crime rates,
etc.)? Which was thought of as the
independent variable and which was the dependent variable?
2) Was the correlation
described in the article an ecological correlation or a correlation between values
for individuals?
3) Was it a positive or
negative correlation? If
mentioned, state the correlation coefficient.
4) Discuss causation. Does the article suggest that the
independent variable caused the dependent variable to increase or
decrease? Is this
plausible? Do you agree?
5) Discuss strengths and
weaknesses of the study. Do you
agree with its conclusions? Why or
why not?
Homework Assignment 9 for Tues,
Sept. 29:
On blackboard
Announcements
Journals due Tues Sept 29. There are 4 journal assignments: 1) class survey data analysis, 2) SAT
scores and family income plus picking colleges and dropout rate, 3)
correlation in meat consumption and height OR in another data set, 4) todayÕs
assignment