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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:. Does background music influence what customers buy?.
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Warm-Up • Grab a half sheet and start working on it! • It says QUIZ at the top, so NO TALKING!
Finding Expected Counts • Expected count for French wine bought when there was no music playing:
Does background music influence what customers buy? • You already have the observed counts… • Fill in the table with expected counts…
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.
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.
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)