Participant Tests Scores
1 A 8
1 B 7
1 C 1
1 D 6
2 A 9
2 B 5
2 C 2
2 D 5
3 A 6
3 B 2
3 C 3
3 D 8
4 A 5
4 B 3
4 C 1
4 D 9
5 A 8
5 B 4
5 C 5
5 D 8
6 A 7
6 B 5
6 C 6
6 D 7

hist.TestA <- ggplot(df, aes(???)) + theme(legend.position = "none") + geom_histogram(aes(y=..density..), colour="black", fill="white", binwidth = 1) + labs(x="Test A", y = "Density") + stat_function(fun = dnorm, args = list(mean = mean(???, na.rm = TRUE), sd = sd(???, na.rm = TRUE)), colour = "black", size = 1)