warm-up grab a half sheet and start working on it! it says quiz at the top, so no talking!
TRANSCRIPT
Warm-Up Grab a half sheet and start working on
it! It says QUIZ at the top, so NO TALKING!
Section 11.2
Finding Expected Counts
Expected count for French wine bought when there was no music playing:
Wine No Music
French Music
Italian Music
Total
French 30 39 30 99
Italian 11 1 19 31
Other 43 35 35 113
Total 84 75 84 243
Does background music influence what customers buy?
You already have the observed counts… Fill in the table with expected counts…
Wine No Music
French Music
Italian Music
Total
French 99
Italian 31
Other 113
Total 84 75 84 243
Chi-Squared test for Homogeneity
The null hypothesis is that the distribution of this categorical variable is the same for all the populations or treatments.
Remember…this is when we are imposing treatments!
What would the hypotheses be for this problem?
Still have to check conditions! For this problem… Random –
Large sample size – each expected count in your table still has to be at least 5.
Independent –
Find chi-squared for the sum of the nine terms
P-value = Conclusion?
Using your calculator Go to STAT and look at the chi-squared
test…it uses matrices! Let’s test the last problem!
Chi-Squared test for association/independence The null hypothesis states that there is
no association between two categorical variables in the population of interest.
: The two categorical variables are independent in the population of interest.
Do angry people have more heart disease? A study followed a random sample of 8474
people with normal blood pressure (and no heart disease) for about 4 years. Each person took and Anger Test to measure how prone a person is to sudden anger. Researchers also recorded whether each person developed coronary heart disease (CHD) below.
Low Anger
Moderate Anger
High Anger
Total
CHD 53 110 27 190
No CHD 3057 4621 606 8284
Total 3110 4731 633 8474
State:
Plan:
Do:
Conclude:
Choose the right test! Are men and women equally likely to suffer
lingering fear from watching scary movies as children? Researched asked a sample of 117 college students to write narratives of their exposure to scary movies before the age of 13.
Fright Symptom
s?
Male Female Total
Yes 7 29 36
No 31 50 81
Total 38 79 117
How to tell? If it is an associations test – does this
variable have anything to do with this other variable – one sample
If it is a homogeneity test – multiple samples(experiments count as multiple samples) – does the distribution of each sample match?
Homework Pg 724 (29-33, 35-41, 44, 50, 53-58)