The table below illustrates the amounts of three different kinds of stones stored in a warehouse,
where the total number of stones is 15 000.
Given that a sample, which includes stones from all 3 kinds, is to be taken from the warehouse, and the number of
stones taken from the third kind is 420, determine the total number of stones in the sample.
When a society to be examined is made up of qualitative sets that have different characteristics, the society should be divided into homogeneous layers according to the characteristics. A researcher should then select a random sample from each layer that is proportional in size to the layer's size in the society. Suppose the total number of stones in the sample from the warehouse is . Solve for as follows.
Thus, the total number of stones that should be in the sample is 900.