Longitudinal Methods

Longitudinal Developmental Design

Repeatedly measuring the same variable over some amount of

time, in one sample or in multiple overlapping samples

Keeping measurement waves spaced over the same amount

of time makes statistical models much more simple

Longitudinal Intervention/ Experimental Design

A design where there are at least two measurement waves,

one before and one after an intervention or experiment. One

group receives the intervention and one group is a control.

in a longitudinal intervention what measurements do you compare to see the effect of the intervention

before and after. it is also important to compare the groups on the first measurement wave to see if there are differences

Quasi-Experimental Longitudinal Design

A design where there are at least two measurement waves,

one before and one after an intervention or experiment. One

group receives the intervention and one group is a control.

The experimenter does not pick which participants are in

which group.

lagged predictor

This predictor now has to explain unique variance in

how the outcome changes from one day to the next day

Advantages of Longitudinal Methods

One of the most valid and powerful ways to study change in

people and in psychological variables

Provides stronger evidence (not causal evidence unless it’s

experimental) for the direction of statistical relationships

important problems

instrument decay, regression to the mean, sample attrition (loss of participants over time), historical/societal effects (An external event may effect variables in some or all of your sample, during the study), testing effects and Normative Developmental Effects (Changes in variables may be due to other factors in lifespan development (e.g., ageing; having children)