Three professors at George Washington University did an experiment to determine if economists are more selfish than other people. They dropped 64 stamped, addressed envelopes with $10 cash in different classrooms on the George Washington campus. 44% were returned overall. From the economics classes 56% of the envelopes were returned. From the business, psychology, and history classes 31% were returned. (
Source: Wall Street Journal )
Let:
= money returned;
= economics classes;
= other classes
Write a probability statement for the overall percent of money returned.
Write a probability statement for the percent of money returned out of the economics classes.
Write a probability statement for the percent of money returned out of the other classes.
Is money being returned independent of the class? Justify your answer numerically and explain it.
Based upon this study, do you think that economists are more selfish than other people? Explain why or why not. Include numbers to justify your answer.
The chart below gives the number of suicides estimated in the U.S. for a recent year by age, race (black and white), and sex. We are interested in possible relationships between age, race, and sex. We will let suicide victims be our population. (
Source: The National Center for Health Statistics, U.S. Dept. of Health and Human Services )
Race and Sex
1 - 14
15 - 24
25 - 64
over 64
TOTALS
white, male
210
3360
13,610
22,050
white, female
80
580
3380
4930
black, male
10
460
1060
1670
black, female
0
40
270
330
all others
TOTALS
310
4650
18,780
29,760
Do not include "all others" for parts (f), (g), and (i).
Fill in the column for the suicides for individuals over age 64.
Fill in the row for all other races.
Find the probability that a randomly selected individual was a white male.
Find the probability that a randomly selected individual was a black female.
Find the probability that a randomly selected individual was black
Find the probability that a randomly selected individual was male.
Out of the individuals over age 64, find the probability that a randomly selected individual was a black or white male.
Comparing “Race and Sex” to “Age,” which two groups are mutually exclusive? How do you know?
Are being male and committing suicide over age 64 independent events? How do you know?
Black females and ages 1-14
No
The next two questions refer to the following: The percent of licensed U.S. drivers (from a recent year) that are female is 48.60. Of the females, 5.03% are age 19 and under; 81.36% are age 20 - 64; 13.61% are age 65 or over. Of the licensed U.S. male drivers, 5.04% are age 19 and under; 81.43% are age 20 - 64; 13.53% are age 65 or over. (Source: Federal Highway Administration, U.S. Dept. of Transportation)
Complete the following:
Construct a table or a tree diagram of the situation.
=
=
=
In words, explain the difference between the probabilities in part (c) and
part (d).
=
Are being age 65 or over and being female mutually exclusive events? How do you know
