Name: _______________ Chi-Square Independence Test
Part 1 – Wondering Walton
Period: _______
Sam Walton wondered if a person’s favorite supermarket had anything to do with their favorite color.
He decided to take a quick survey where he recorded each person’s favorite color and each person’s favorite store. He placed the results in a table, as shown in the “Observed Table” below. Then, he started to analyze the data…
Walmart
Target
HEB
Total
Red
2
3
8
Observed Table
Blue Green
3
7
2
2
3
1
Purple
2
1
1
Total
Red
Expected Table
Blue Green Purple Total
Walmart
Target
HEB
Total
1.
Find the total amounts for each row and column. Also, determine the total amount of people surveyed (the sample size). Record the answer in the “Observed Table” above.
2.
Using the data from the observed table, find the probability that a person would prefer each color and each store. For example, the probability that someone would prefer red would be equal to the sum of the people that said red was their favorite color divided by the sample size.
Record these probabilities in the “Expected Table.”
3.
Using the probabilities calculated in step 2, find the probability that a person would prefer every combination of the colors and the stores, i.e. the probability that someone prefers both the color red and the store Walmart. You may assume that these are independent events, and that you may use the equation: P(A and B) = P(A) * P(B). Record your answers in the “Expected
Table.”
4.
Find the expected value of each combination by multiplying the expected probability by the sample size and rounding to the nearest whole number.
5.
Using both the “Observed Table” and the “Expected Table,” perform a Chi Square Independence
Test. This can be found after pressing the “STAT” button of your calculator and moving over to tests. You may also need to access the Matrix screen by pressing “2ND" and “X -1 ” and then moving over to “EDIT.” [Continue on the back]

Name: _______________ Chi-Square Independence Test Period: _______
Use the following spaces to fill out the information needed for your Chi-Square Independence Test:
Null Hypothesis: ________________________________________________________________
Alternative Hypothesis: __________________________________________________________
Alpha-Level: _______________
P-Value: __________________
Conclusion: ____________________________________________________________________
______________________________________________________________________________
Dracula is feeling quite anxious about Halloween this year. He doesn’t know what he should wear to the annual Halloween Ball. His ghoulfriend thinks he should wear yellow, but he is worried that vampires don’t look good in yellow. His mummy thinks that he should wear purple, but he is worried that purple is more of a Frankenstein’s monster kind of color. You have decided to help him out! Conduct a Chi Square
Independence Test to determine if the color he wears affects whether monsters like him or not.
Vampires
Frankenstein’s
Monster
Total
Yellow
3
20
23
Observed Table
Purple
41
42
83
Black
74
14
88
Total
118
76
194
Vampires
Frankenstein’s
Monster
Total
Yellow
Expected Table
Purple Black Total
Null Hypothesis: ________________________________________________________________
Alternative Hypothesis: __________________________________________________________
Alpha-Level: _______________
P-Value: __________________
Conclusion: ____________________________________________________________________
______________________________________________________________________________