For a recent project, we have been working with a lot of Likert scale data (e.g. “strongly disagree”, “disagree”, “neutral”, “agree”, “strongly agree”). Many times we are averaging several questionnaire items into a summary score e.g. generate myaverage = (Q1 + Q2 + Q3)/3.
I’ve been thinking about the best way to visualize these distributions of scale scores. Stata offers histograms, kernel densities and dotplots, none of which seem 100% intuitive or satisfactory. dotplots are intuitive in that every person is represented by a dot, but the fact that they are turned sideways in Stata seems unsatisfactory and counter-intuitive to me.
clear all // clear data
set obs 100 // 100 observations
generate myaverage = runiform(1, 5) // randomly simulated score
histogram myaverage
graph export "myhistogram.png", replace
kdensity myaverage
graph export "mydensity.png", replace
dotplot myaverage
graph export "mydotplot.png", replace
stripplotI’ve come to like stripplot (Cox, 2003) as a more intuitive alternative to the above plots. stripplot requires a few options to make the plot I want, but is very useful.
stripplot myaverage, ///
stack /// stack the dots
width(1) /// bin with width 1
msymbol(circle) /// symbols are circles
title("Scale 1") /// title
xtitle("Scale 1") /// title for x axis
xlabel(1 "strongly disagree" 2 "disagree" 3 "neutral" 4 "agree" 5 "strongly agree", labsize(vsmall)) // customize labels
graph export "mystripplot.png", replace
The width of the bins that stripplot uses can be adjusted with the width() option to adjust the resolution of the graph.
stripplot myaverage, stack width(.25) msymbol(circle)
graph export "mystripplotA.png", replace
stripplot myaverage, stack width(.5) msymbol(circle)
graph export "mystripplotB.png", replace
stripplot myaverage, stack width(1) msymbol(circle)
graph export "mystripplotC.png", replace
width(.25)
width(.5)
width(1)