A comparison was made between the total bacteria counts obtained from swabs taken from two designs of telephone mouthpiece, A and B. Both mouthpieces were subjected to two months’ use by randomly selected volunteers so that all headpieces received the same amount of use. Given that the data are not normally distributed, determine whether the level of bacterial contamination ascertained by the swabs differed between the two designs.

Total bacterial counts (´ 105):

Design A: 6.8   3.2 10.9 7.8 4.1 12.1 15.7 1.1   3.7 8.4   9.6 10.6 8.9   5.4  2.0

Design B: 8.7 14.4 15.1 2.9 6.8 14.8 11.3 6.3 18.0 1.1 13.1 14.3 9.4 13.7 15.6

What will be the appropriate test for this test?

Select one:

a. Paired Sample t Test

b. Wilcoxon’s Test

c. Independent two sample t test

d. Mann-Whitney Test

What is the calculated test statistics value in this test?

Select one:

a. 160

b. 208

c. 185

d. 280

Which of the following conclusion is correct?

Select one:

a. The level of bacteria in both designs is equal. 

(critical statistics = 161 > calculated statistics, p > 0.05).

b. The level of bacteria in both designs is equal. 

(critical statistics = 141 > calculated statistics, p > 0.05).

c. The level of bacteria in both designs is not equal 

(critical statistics = 141 > calculated statistics, p < 0.05).

d. The level of bacteria in both designs is not equal 

(critical statistics = 161 > calculated statistics, p < 0.05).