Question 2 An airline wishes to choose between two alternative methods for evacuating its aircraft in the event of an emergency. One major concern is the evacuation time. In a study, an evacuation simulation was performed 10 times, 5 times using Method A and 5 times using Method B. The evacuation times of each method were as given below.

Evacuation Time (seconds)

Method A 61 59 67 40 83

Method B 63 69 77 54 87

(a) Use an independent samples -test to test whether or not there is a significant difference between the evacuation times of the two methods.

(b) What assumptions, if any, do you need to make for the above test to be the correct test to use?

(c) Suppose that five aircrews were involved in the study. Each aircrew performed two evacuation simulations, one of each method. Each column now represents a pair of Method A and B evacuation times for each of the five aircrews. For example, the first evacuation time for method A (i.e. 61) and the first evacuation time for method B (i.e. 63) were conducted by the first aircrew, and so on. Revise your statistical test and your conclusions in the light of this new information. State clearly any additional assumptions that you need to make.