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Week 4
15.18 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 α = .01, is the degree of certainty independent of credits earned? Certaint Credits Earned | Very Uncertain | Somewhat certain| Very Certain| Row Total| 0–9 | 12| 8| 3| 23|

10 to 59| 8| 4| 10| 22|
60 or more| 1| 7| 11| 19|
Col Total| 21| 19| 24| 64|
 |  |  |  |  |  |  |
Chi-square Contingency Table Test for Independence|
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| | | | |
| | | Col 1 | Col 2 | Col 3 | Total |
| Row 1| Observed | 12 | 8 | 3 | 23 |
| | Expected | 7.55 | 6.83 | 8.63 | 23.00 |
| Row 2| Observed | 8 | 4 | 10 | 22 |
| | Expected | 7.22 | 6.53 | 8.25 | 22.00 |
| Row 3| Observed | 1 | 7 | 11 | 19 |
| | Expected | 6.23 | 5.64 | 7.13 | 19.00 |
| Total| Observed | 21 | 19 | 24 | 64 |
| | Expected | 21.00 | 19.00 | 24.00 | 64.00 |
| | | | | | |
| | | 14.76| chi-square| | |
| | | 4| df| | |
| | | .0052| p-value| | |
| | | | |
15.22 A student team examined parked cars in four different suburban shopping malls. One hundred vehicles were examined in each location. Research question: At α = .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-size van| 2| 3| 3| 2| 10|
SUV| 19| 27| 26| 12| 84|
Truck| 14| 6| 17| 9| 46|
Co Total| 100| 100| 100| 100| 400|
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| | | | | | | |
Chi-square Contingency Table Test for Independence| |
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| | | | |
| | | Col 1 | Col 2 | Col 3 | Col 4 | Total |
| Row 1| Observed | 44 | 49 | 36 | 64 | 193 | | | Expected | 48.25 | 48.25 | 48.25 | 48.25 | 193.00 | | Row 2| Observed | 21 | 15 | 18 | 13 | 67 |
| | Expected | 16.75 | 16.75 | 16.75 | 16.75 | 67.00 | | Row 3| Observed | 2 | 3 | 3 | 2 | 10 |
| | Expected | 2.50 | 2.50 | 2.50 | 2.50 | 10.00 | | Row 4| Observed | 19 | 27 | 26 | 12 | 84 |
| | Expected | 21.00 | 21.00 | 21.00 | 21.00 | 84.00 | | Row 5| Observed | 14 | 6 | 17 | 9 | 46 |
| | Expected | 11.50 | 11.50 | 11.50 | 11.50 | 46.00 | | Total| Observed | 100 | 100 | 100 | 100 | 400 | | | Expected | 100.00 | 100.00 | 100.00 | 100.00 | 400.00 | | | | | | | | |

| | | 24.53| chi-square| | | |
| | | 12| df| | | |
| | | .0172| p-value| | | |
| | | | | | | |
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15.24 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 α = .05, is the cockpit noise level independent of flight phase? (Data are from

Capt. Robert E. Hartl, retired.) Noise

Noise Level| Climb| Cruise| Descent| Total|
Low| 6| 2| 6| 14|
Medium| 18| 3| 8| 29|
High | 1| 3| 14| 18|
Col Total | 25| 8| 28| 61|
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 |  |  |  |  |  |  |
Chi-square Contingency Table Test for Independence|
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| | | Col 1 | Col 2 | Col 3 | Total |
| Row 1|...
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