Question

A staff psychologist at a police precinct developed a week-long training course designed to improve on the job sensitivity of police officers. The psychologist designs a study where some policemen randomly get and complete the course. A month later the psychologist records the number of domestic disputes the police officers successfully resolved from their police reports. What can the psychologist conclude with an α of 0.05. The success data are below.

no course	course
11.2 12.5 10.6 12.7 8.3 15.6 12.1	14.8 16.3 14.3 17.4 11.2 16.5 15.4

a) What is the appropriate test statistic?
---Select--- na z-test One-Sample t-test Independent-Samples t-test Related-Samples t-test

b)
Condition 1:
---Select--- no course police precinct domestic disputes completing the course job sensitivity
Condition 2:
---Select--- no course police precinct domestic disputes completing the course job sensitivity

c) Compute the appropriate test statistic(s) to make a decision about H₀.
(Hint: Make sure to write down the null and alternative hypotheses to help solve the problem.)
p-value =  ; Decision:  ---Select--- Reject H0 Fail to reject H0

d) , compute the corresponding effect size(s) and indicate magnitude(s).
If not appropriate, input and/or select "na" below.
d =  ;   ---Select--- na trivial effect small effect medium effect large effect
r² =  ;   ---Select--- na trivial effect small effect medium effect large effect

e) Make an interpretation based on the results.

Participants that received training had significantly less resolved domestic disputes than those that did not receive training.

Participants that received training had significantly more resolved domestic disputes than those that did not receive training.  

  Participants that received training did not differ significantly on resolved domestic disputes than those that did not receive training.

Answer 1

The appropriate test for given data is paired t test.

Null hypothesis: There is no true mean difference between job sensitivity of police officers before and after training course.

Alternate hypothesis: There is true mean difference between job sensitivity of police officers before and after training course.

The R program for testing this problem is:

> nc<-c(11.2,12.5,10.6,12.7,8.3,15.6,12.1);
> c<-c(14.8,16.3,14.3,17.4,11.2,16.5,15.4);
> t.test(nc,c,paired=TRUE,alternative="two.sided")

Paired t-test

data: nc and c
t = -7.3264, df = 6, p-value = 0.0003304
alternative hypothesis: true difference in means is not equal to 0
95 percent confidence interval:
-4.364045 -2.178813
sample estimates:
mean of the differences
-3.271429

>
Here P value is less than 0.05. So, we reject null hypothesis and conclude that

There is true mean difference between job sensitivity of police officers before and after training course.

The training course is effective for Police Officers.