Question

when is randomised complete block design appropriate for an experiment?

Answer 1

In this designs, blocks are homogeneous groups of units . In the experimental fields or units, where variation(fertility gradient in agricultural experiments) is in one direction, it makes sense to divide the fields into groups of homogeneous units called blocks. As the name suggests, the block is a complete replicate .That is a block will contain all the treatments .

It is also the design where local control concept is fully applied. So a completely randomized design is appropriate when variation between blocks is more and variation within blocks (homogeneous) is less.