Title: Symmetric Morse Code Confusions

Source: Rothkopf (1957)
 
Description: 
Confusion percentages between Morse code signals. The scores are 
confusion rates on 36 Morse code signals (26 for the alphabet; 10 
for the numbers 0,...,9). Each Morse code signal is a sequence of 
up to five 'beeps'. The beeps can be short (0.05 sec) or long 
(0.15 sec), and, when there are two or more beeps in a signal, 
they are separated by periods of silence (0.05 sec).

Rothkopf asked 598 subjects to judge whether two signals, 
presented acoustically one after another, were the same or not. 
The values are the average percentages with which the answer 'Same!' was 
given in each combination of row stimulus i and column stimulus 
j, where either i or j was the first signal presented. These 
data are similarities and the table is symmetric with zero 
diagonal values.


The morse codes are:

A  .-
B  -...
C  -.-.
D  -..
E  .
F  ..-.
G  --.
H  ....
I  ..
J  .---
K  -.-
L  .-..
M  --
N  -.
O  ---
P  .--.
Q  --.-
R  .-.
S  ...
T  -
U  ..-
V  ...-
W  .--
X  -..-
Y  -.--
Z  --..
1  .----
2  ..---
3  ...--
4  ....-
5  .....
6  -....
7  --...
8  ---..
9  ----.
0  -----