Question

Suppose I was to   1. randomly choose a twig and then 2.  measure all leaves on the twig.  What is this method of sampling called?  Suggest an advantage and a disadvantage of this approach.          

Answer 1

This is called a cluster sample.

An advantage of this approach is that it is very easy, cost- efficient and time-efficient to collect leaves (sample). Moreover the leaves near the end are smaller than leaves further up, so cluster sampling will enable to include leaves of every size and ages in our sample.

A disadvantage is that we are getting leaves from a particular part only not from the whole tree and in turns fail to reflect the diversity in the sampling frame. It is not very representative and can give misleading results if the twig we choose is completely different from other twigs of tree. Moreover selected twig may has leaves more than needed which can affect the tree.