Question

One criticism of racial profiling studies is that people’s driving frequency is often unaccounted for. This is a problem because, all else being equal, people who spend more time on the road are more likely to get pulled over eventually. The following table contains PPCS data narrowed down to black male respondents. The variables measure driving frequency and whether these respondents had been stopped by police for traffic offenses within the past 12 months. With an alpha of .01, conduct a five-step hypothesis test to determine if the variables are independent.

Driving Frequency	Yes	No	Raw Marginal
Almost Every Day	214	946	1,160
Often	32	238	270
Rarely	6	360	366
Column Marginal	252	1,544	N = 1,796

Answer 1

Null hypothesis, H₀: the variables i.e. respondents had been stopped by police for traffic offenses within the past 12 months and Driving Frequency are independent

Alternative hypothesis, H₁: the variables are not independent.

Observed Frequencies:

Driving Frequency	Yes	No	Raw Marginal
Almost Every Day	214=O11	946=O12	1,160=O10
Often	32=O21	238=O22	270=O20
Rarely	6=O31	360=O32	366=O30
Column Marginal	252=O01	1,544=O02	1,796=N

Expected frequencies:

Driving Frequency	Yes	No
Almost Every Day	162.7617=E11	997.2383=E12
Often	37.8842=E21	232.1158=E22
Rarely	51.3541=E31	314.6459=E32

Hence there is insufficient evidence to conclude that the variables are independent.