Matched groups of 4, based on initial assessment of pain tolerance.

  Pain relief score
Tolerance
group
  Control   Codeine
only
Acupuncture
only
Codeine +
Acupuncture
1
2
3
4
5
6
7
8
0.0
0.3
0.4
0.4
0.6
0.9
1.0
1.2
0.6
0.7
0.8
0.9
1.5
1.6
1.7
1.6
0.5
0.6
0.8
0.7
1.0
1.4
1.8
1.7
1.2
1.3
1.6
1.5
1.9
2.3
2.1
2.4

This page gives three different examples of randomised block data.

The first example is artificially blocked using matched groups of 4. In the others, the blocks are natural groupings.

Note that the final example has two replicates for each treatment in each block.

Acupuncture and Codeine for dental pain relief
An anaesthetist conducted an experiment to assess the effects of codeine and acupuncture for relieving dental pain. The experiment used 32 subjects who were grouped into blocks of 4 according to an initial assessment of their tolerance to pain. Pain relief scores were recorded from each subject two hours after dental treatment. The experiment was double blind since neither the subjects nor the person assessing pain relief knew which treatment had been adminstered.
Clotting time of plasma
Plasma was taken from eight subjects. Four samples of plasma were obtained from each subject and they were treated in four different ways before the clotting time (min)was measured.
Effect of cultivar on plant height
An experiment was conducted to compare the differences in growth among four different cultivars of a house plant. The greenhouse had three benches in different locations which form natural blocks. Two pots of each cultivar were randomly assigned to each bench for a total of six pots per cultivar and eight pots per bench.