Statistical Procedure

This procedure can be used when the:

Outcome (Dependent) variable is a Continuous and Normally distributed measure
Exposure (Independent) variable is 2 independent groups

Present this graphically using a Box and Whisker Plot

In SPSS select: Graphs > Chart Builder - Gallery – Boxplot | Simple Boxplot

Analyse this in SPSS using:

Analyze >Compare Means > Independent-Samples T Test

Report this quoting the:

Mean Difference, 95% Confidence Intervals and p-value
Use the confidence intervals output by SPSS

Comments

Use the statistics for Equal Variances assumed if the SDs of the groups are similar, if not use Equal Variances not assumed.

For small samples a Scatter plot using the Grouping variable as the X-axis and the Y axis for the variable might be useful.

References

Chapter 9, p 334 in Discovering Statistics using SPSS 3rd Edition, A. Field, Sage Publications (2009) (ISBN: 9781847879073)
Testing for Differences between groups in the Statistics for the Terrified package

Please Report any issues to Brian Yuen