Tag: Group Statistics

Quant: Group Statistics in SPSS

Introduction

The aim of this analysis is to make a decision about whether a person is alive or dead ten years after a coronary is reflected in a significant difference in his diastolic blood pressure taken when that event occurred. The variable “DBP58” will be used as a dependent variable and “Vital10” as an independent variable.

From the SPSS outputs the goal is to:

  • Analyze these conditions to determine if there is a significant difference between the DBP levels of those (vital10) who are alive 10 years later compared to those who died within 10 years.

Hypothesis

  • Null: There is no basis of difference between the DBP58 and Vital10
  • Alternative: There is are real differences between the DBP58 and Vital10

Methodology

For this project, the electric.sav file is loaded into SPSS (Electric, n.d.).  The goal is to look at the relationships between the following variables: DBP58 (Average Diastolic Blood Pressure) and Vital10 (Status at Ten Years). To conduct a parametric analysis, navigate to Analyze > Compare Means > Paired-Samples T Test.  The variable DBP58 was placed in the “Test Variables” box, and Vital10 was placed under “grouping variable” box.  Then select the “Define Groups” button and enter 0 for “Group 1” and 1 for “Group 2”.  The procedures for this analysis are provided in video tutorial form by Miller (n.d.). The following output was observed in the next two tables.

Results

Table 1: Group Statistics

Status at Ten Years N Mean Std. Deviation Std. Error Mean
Average Diast Blood Pressure 58 Alive 178 87.56 11.446 .858
Dead 61 92.38 16.477 2.110

According to the results in Table 1, the mean diastolic blood pressure of those who have passed away ten years later was 5 points higher and had a huge standard deviation.  Thus, those who are alive ten years later have a smaller variation of their diastolic blood pressure.

Table 2: Independent Samples Test

Levene’s Test for Equality of Variances t-test for Equality of Means
F Sig. t df Sig. (2-tailed) Mean Difference Std. Error Difference 95% Confidence Interval of the Difference
Lower Upper
Average Diast Blood Pressure 58 Equal variances assumed 8.815 .003 -2.515 237 .013 -4.815 1.915 -8.587 -1.043
Equal variances not assumed -2.114 80.735 .038 -4.815 2.277 -9.347 -.284

According to the independent t-test for equality of means, shows that there is no equality in the variance at the 0.05 level, such that when equal variances are not assumed, the null hypothesis could be rejected at the 0.05 level because the significance value is 0.038.  Thus, there is a statistically significant difference between the means of diastolic blood pressure of those who are alive and those who have passed away.

SPSS Code

DATASET NAME DataSet1 WINDOW=FRONT.

T-TEST GROUPS=vital10(0 1)

  /MISSING=ANALYSIS

  /VARIABLES=dbp58

  /CRITERIA=CI(.95).

References: