4.3 Some Basic Considerations in Experimental Design
The design and analysis of experiments is an extensive subject to which numerous books
have been entirely devoted (Davies, 1954; Cochran and Cox, 1957). The problems of
design are of course inseparable from those of analysis and it is worth emphasizing that
unless a suitable design is employed, it may be very difficult or even impossible to obtain
valid conclusions from the resulting data.
Statistical experimental design was founded in the early 1920s by R.A.Fisher, working
at an agricultural research station at Rothamsted, England, where work such as
comparing the yield from several varieties of wheat was performed. However, so many
other factors were involved, such as temperature, humidity, position in field and so on,
that unless the experiment was carefully designed, it would have been impossible to
separate the effects of the different varieties of wheat from the effects of other variables.
Fisher identified three important principles of experimental design: replication,
randomization and blocking.