ECON 230
Lab 3
The goal of this lab is to understand and find simple probabilities and conditional
probabilities, and to use the Multiplication Rule and the Addition Rule.
Part 1: Create a table with your qualitative variable V1 and
quantitative variable V2.
(2 points)
For your Qualitative Variable, return to Lab 2 and choose the largest slice of the pie
graph to label the first column. Label the second column “others”.
For your Quantitative Variable, V2, label the first row LOW to indicate values that are
at “the median or lower.” Label the second row as HIGH to indicate values that are
“higher than the median.” You found the median in Lab 2.
For a student who has more high literacy countries than any other type, the chart will
look like:
Qualitative Variable, V1 (literacy)
Quantitative
Variable, V2
(Life expectancy)
For the data in the chart, this student has 22 high literacy countries, 9 of which have
low values for life expectancy and 13 of which have high values for life expectancy.
This student has 18 countries which are not high literacy, 10 of which have low
values for life expectancy and 8 of which have high values for life expectancy.
If there is a tie between high and low literacy for the most common category, choose
high as the most common category. If there is a tie between high and medium
literacy for the most common category, choose high as the most common category. If
there is a tie between medium and low literacy for the most common category, choose
medium as the most common category.
Look at your data and count up the observations for each of the four cells in the table.
Place the sums in each cell and be sure that the numbers in all of the cells sum to 40.
Also record the sums for each row and each column.
Part 2: Find simple probabilities.
(1 point each)
A. Compute the probability of being in Row 1. (For example, P(low value for life
expectancy)).
B. Compute the probability of being in Column 1. (For example, P(high literacy)).
1
High Others
Low 9 10
High 13 8
