43 Within vs Between / Contextual Effects Visualization
Within, between, and contextual effects can be a challenge to think about or visualize. This shiny app allows you to explore different effects to build intuition about what these relationships mean, substantively, using students in schools as a context. In the graph, the big dots and black dashed line represent school means, that is, the between effect. The small dots and the multicolored lines represent individual schools, or, the within effect. The contextual effect is the difference in within and between effects (sort of like an interaction representing a “difference in slopes”). By default, it is set to 0, so the within and between effects are the same, which is the assumption of the random intercepts model. (NB The “offset” parameter is not a real MLM parameter; it just spreads out the school means on the x-axis to make the visualization more powerful)
Exercises:
Before manipulating a slider, make a prediction for what will change in the graph, then verify by moving the slider
Select parameters to generate a between effect of 0 and a within effect of 0.5
Select parameters to generate a between effect of 0.5 and a within effect of 0
Imagine that the clusters are people and the observations are measurements. What would the graph look like if the x-axis represented typing speed and the y-axis represented typing accuracy?
Using the within/between HSB examples, input the parameter estimates from the Mundlak model into the shiny app and compare that to our visualization of the data here.