Chi square test in different practical applications

1. Sixty-four students in an introductory college economics class were asked how many credits they had earned in college, and how certain they were about their choice of major. Research question: At alpha = .01, is the degree of certainty independent of credits earned? Certainty
Credits Earned Very Uncertain Somewhat Certain Very Certain Row Total
0-9 12 8 3 23
10-59 8 4 10 22
60 or more 1 7 11 19
Col Total 21 19 24 64

2. A student team examined parked cars in four different suburban shopping malls. One hundred vehicles were examined in each location. Research question: At alpha = .05, does vehicle type vary by mall location? (Data are from a project by MBA students Steve Bennett, Alicia Morais, Steve Olson, and Greg Corda.) Vehicles
Vehicle Type Somerset Oakland Great Lakes Jamestown Row Total
Car 44 49 36 64 193
Minivan 21 15 18 13 67
Full-sized Van 2 3 3 2 10
SUV 19 27 26 12 84
Truck 14 6 1 9 46
Col Total 100 100 100 100 400

3. High levels of cockpit noise in an aircraft can damage the hearing of pilots who are exposed to this hazard for many hours. A Boeing 727 co-pilot collected 61 noise observations using a handheld sound meter. Noise level is defined as "Low" (under 88 decibels), "Medium" (88 to 91 decibels), or "High" (92 decibels or more). There are three flight phases (Climb, Cruise, Descent). Research question: At alpha = .05, is the cockpit noise level independent of flight phase? (Data are from Capt. Robert E. Hartl, retired.) Noise
Noise Level Climb Cruise Descent Row Total
Low 6 2 6 14
Medium 18 3 8 29
High 1 3 14 18
Col Total 25 8 28 61

4. In a study of childhood asthma, 4,317 observations were collected on education and smoking during pregnancy, shown in the 4 × 3 contingency table below. Research question: At alpha = .005, is smoking during pregnancy independent of education level? (Data are from Michael Weitzman and Deborah Klein Walker, "Maternal Smoking and Asthma," Pediatrics 85, no. 4 [April 1990], p. 507.) Pregnancy

Education No Smoking < 12 Pack = 12 Pack Row Total
<High School 641 196 196 1,033
High School 1,370 290 270 1,930
Some College 635 68 53 756
College 550 30 18 598
Col Total 3,196 584 537 4,317