AT&T would like to investigate if brand of smartphone and income level are indep

Question

AT&T would like to investigate if brand of smartphone and income level are independent variables. The following contingency table shows the number of customers who own three brands of smartphones along with their income level.

excel file with table data: 12-Q9_10_Smartphone_Brands.xlsx

The expected number of customers who own a Motorola smartphone and earn between $50,000 and $100,000 is ________.

Question 9 options:

10.0

18.0

31.5

40.5

Smartphone Income Level iPhone Samsung Motorola Less than $50,000 15 20 15 $50,000-$100,000 15 50 25 More than $100,000 10 20 30

Explanation / Answer

The row total for the income 50k-100k is 90.

The column total for Motorola is 70.

The overall total is 200.

Hence,

E(Mot and 50k-100k) = (row total)*(column total)/overall = 90*70/200 = 31.5 [ANSWER, C]

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