Homework Module 3 pt.3

The United States National Transportation Safety Board was interested in whether, on average, the severity of head injuries sustained in car crashes differed between the sizes of the vehicle driven.The size of vehicle was categorised into four types: Light, Medium, Heavy and Van. 175 randomly chosen vehicles, each containing a crash-test dummy, were driven into a wall at 55 kph and a severity of head injury score was recorded, where the higher the score the more severe the head injury.

The F?test computer output from SPSS required for some parts of the questions below:

ANOVA Head injury Sum of Squares df Mean Square F Sig. Between Groups 5316986.017 3 1772328.672 8.117 000 Within Groups 37335777.160 171 218337.878 Total 42652763.177 174 Multiple Comparisons Dependent Variable: Head injury Turkey HSD Mean 95% Confidence Interval (1) Vehicle size (J) Vehicle size Difference (1-J) Sid, Error Sig, Lower Bound Upper Bound Light Medium 85.943 82.191 723 -127.30 299.19 Heavy -11.638 136.332 1.000 -365.35 342.07 Van -417.347" 101.335 000 -680.26 -154.44 Medium Light -85.943 82. 191 723 -299.19 127.30 Heavy -97.581 139.140 896 -458.58 263.41 Van -503.291" 105.083 000 -775.93 -230.66 Heavy Light 11.638 136.332 1.000 -342.07 365.35 Medium 97.581 139. 140 896 -263.41 458.58 Van -405.710' 151.240 040 -798.10 -13.32 Van Light 417.347 101.335 000 154 44 680.26 Medium 503.291" 105.083 000 230.66 775.93 Heavy 405.710" 151.240 040 13.32 798.10 *. The mean difference is significant at the 0.05 level