Music and work efficiency

  Efficiency rating  
Employee   Before music     After music   Difference
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
21
35
40
38
23
27
28
39
22
35
28
20
39
28
34
32
35
38
57
37
30
39
28
40
48
33
33
39
41
40
11
0
-2
19
14
3
11
-11
18
13
5
13
0
13
6

Is the mean of the differences zero?


Use the examples on this page to introduce the idea of paired data. Explain that we can answer questions about whether the means of the two variables are the same by analysing the differences (as a univariate data set).

Music and work efficiency

Does music in a warehouse affect productivity? Efficiency ratings of 15 employees recorded before and after the music system was installed.

Environment and IQ of identical twins

Identical twins are genetically the same, so any differences are caused by their environment (or experimental treatment for animals). The table below shows the IQs of ten pairs of twins who were raised apart — one in a 'good' environment and the other in a 'poor' environment.

Repair estimates from two garages

Measurements may be paired by other mechanisms. An insurance company is concerned that garage A is charging too much for repairing damage to cars. Ten damaged cars were taken to both garage A and another garage for estimates.