Theory, Examples & Exercises
Rothkopf (1957), data used here were distilled from library
The aim of the study was to show, which Morse codes are the most easy to be confused. Each Morse code is a set of short (0.05 sec) and/or long (0.15 sec) beeps. Experiment was joined by 598 respondents, and Rothkopf played each of them different combinations of Morse codes, separated by short pause. Each respondent should quickly decide, whether the played codes were the same or different. The result is confusion matrix, in which each number represents number of cases when respondents consider the given combination of codes to be different. The higher the number, the easier are the codes recognisable.
Example of the matrix goes like this:
morse.dist <- read.delim ('https://raw.githubusercontent.com/zdealveindy/anadat-r/master/data/morsecodes-dist.txt', row.names = 1, head = T)
Rothkopf, E. Z. (1957): A measure of stimulus similarity and errors in some paired-associate learning tasks. Journal of Experimental Psychology, 53:94–101.