Design: The design is a 2 (birth order) x (2) (reaction time) mixed ANOVA:
IV (between-subjects) = Birth order (1st/Subsequent)
IV (within-subjects) = Hand (dominant/non-dominant)
DV = Reaction time
Do reaction times different between first-born and subsequently born people (between-subjects main effect)?
Do reaction times differ between the dominant and non-dominant hand (within-subjects main effect)?
Is there an interaction between hand and whether people are first-born for reaction times?
Create a composite score of the within-subjects variable in order to be able to get the marginal total descriptives
Via Analyse - Descriptives - Means
Graphing: Clustered bar chart, clustered error-bar chart, and line graphs could be useful, but only present one in a Results section.
Analysis: Analyze - General Linear Model - Repeated measures - Specify the within-subject factor as Hand with 2 levels, then Define and add First-born as a between-subjects factor - Plots (optional) - Options (Descriptive statistics, Effect sizes, Power, Homogeneity tests)