Question

A health educator wants to evaluate the effect of a safety film on the frequency with which children wear their bicycle helmets. Eight (8) children are selected for the experiment. First, a baseline number of times the children wear their helmets is measured over the period of a month. Next, the same children are shown a safety film and again the researcher measures the number of times the children wear their helmets in the month following the film. The health educator wanted to know if watching the film changed the frequency of wearing bicycle helmets. The following data are collected: Child 1 2 After Film 28 31 Before Film 2028 3 4 5 6 19 30 25 2030_21 7 28 23 8 32 25 27 22

Answer 1

Solution:

Question 18

The appropriate statistical test for this study is paired t-test or dependent samples t-test.

Question 19

Here, we have to use paired t test.

The null and alternative hypotheses for this test are given as below:

Null hypothesis: H0: Watching the safety film does not change the frequency of wearing bicycle helmet.

Alternative hypothesis: Ha: Watching the safety film changes the frequency of wearing bicycle helmet.

Question 20

The required null and alternative hypotheses are given as below:

H0: µd = 0 versus Ha: µd ≠ 0

This is a two tailed test.

Question 21

Test statistic for paired t test is given as below:

t = (Dbar - µd)/[Sd/sqrt(n)]

From given data, we have

Dbar = 3.8750

Sd = 3.1368

n = 8

df = n – 1 = 7

α = 0.05

t = (Dbar - µd)/[Sd/sqrt(n)]

t = (3.8750 – 0)/[ 3.1368/sqrt(8)]

t = 3.4941

Question 22

We are given

α = 0.05

Test is two tailed test.

Critical values = -2.3646 and 2.3646

(by using t-table)

Question 23

Test statistic value is outside the critical values.

So, we reject the null hypothesis.

There is sufficient evidence to conclude that watching the safety film changes the frequency of wearing bicycle helmet.