Question

Statistics for Nursing Research 3rd edition Grove and Cipher

A randomized experimental study examined the impact of a special type of vocational rehabilitation on employment variables among spinal-cord injured veterans, in which post-treatment wages and hours worked were examined (Ottomanelli, Goetz, Suris, McGeough, Sinnott, Toscano, Barnett, Cipher, Lind, Dixon, Holmes, Kerrigan, & Thomas, 2012). Participants were randomized to receive supported employment or treatment as usual (“Control”). Supported employment refers to a type of specialized interdisciplinary vocational rehabilitation designed to help people with disabilities obtain and maintain community-based competitive employment in their chosen occupation (Bond, 2004).

A subset of simulated data from this study are presented in HW5.sav. The independent variable in this example is treatment group (Supported Employment Vocational Rehabilitation Versus Control), and the dependent variable was the amount of weekly wages earned post-treatment. The null hypothesis is “There is no difference between the treatment and control groups in post-treatment weekly wages earned among veterans with spinal cord injuries.”

1.Compute an independent samples t-test using “Group” as the independent variable and “Wages” as the dependent variable. List the numerator value. Hint: No hand calculations are required for Q1 and 2. The values are found in the output.

2.List the denominator value.

Data from excel:

column 1:

"ID"

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20

Column 2

"Group"

0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1

"wages"

$75
$70
$125
$140
$200
$165
$149
$75
$150
$135
$200
$225
$157
$165
$330
$210
$330
$290
$250
$170

Answer 1

Result:

1.Compute an independent samples t-test using “Group” as the independent variable and “Wages” as the dependent variable. List the numerator value. Hint: No hand calculations are required for Q1 and 2. The values are found in the output.

Calculated t= -4.22, P=0.001 which is < 0.05 level of significance. Ho is rejected.

We conclude that there is a difference between the treatment and control groups in post-treatment weekly wages earned among veterans with spinal cord injuries.

2.List the denominator value for test statistic t.

denominator value is pooled sd/sqrt(2/10)=55.3*SQRT(2/10)

=24.73

MINITAB output:

Two-Sample T-Test and CI: "wages", "Group"

Method

μ₁: mean of "wages" when "Group" = 0

µ₂: mean of "wages" when "Group" = 1

Difference: μ₁ - µ₂

Equal variances are assumed for this analysis.

Descriptive Statistics: "wages"

"Group"	N	Mean	StDev	SE Mean
0	10	128.4	43.0	14
1	10	232.7	65.3	21

Estimation for Difference

Difference	Pooled StDev	95% CI for Difference
-104.3	55.3	(-156.3, -52.3)

Test

Null hypothesis	H₀: μ₁ - µ₂ = 0
Alternative hypothesis	H₁: μ₁ - µ₂ ≠ 0

T-Value	DF	P-Value
-4.22	18	0.001