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 infielders (IF) than any other position, the table will look
like:
Qualitative Variable, V1 (position)
Quantitative
Variable, V2
(slugging percentage)
For the data in the chart, this student has 22 infielders, 9 of whom have low values for
slugging percentage and 13 of whom have high values for slugging percentage. This
student has 18 players who are not infielders, 10 of whom have low values for
slugging percentage and 8 of whom have high values for slugging percentage.
If there is a tie between IF and OF for the most common category, choose IF as your
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 slugging
percentage)).
B. Compute the probability of being in Column 1. (For example, P(infielder)).
C. Compute the probability of being in Row 1 and Column 1 using the appropriate
frequency from your table. (For example, P(infielder who has low slugging
percentage)).
1
IF Others
Low 9 10
High 13 8
