3 sub-categories in snowball sampling:

  1. Linear snowball sampling

The chain grow linearly. Each member in the sample refers to one more member.

  1. Exponential non-discriminative snowball sampling

One to many relationships. Each member in the study refers to multiple members, and all are selected in the study. As you can imagine, this creates an exponential effect on the size of the sample. As you might have guessed, this may introduce bias into the sampling and researchers have no idea if the sample is representative of the population under study.

  1. Exponential discriminative snowball sampling

Here, while we will request the member to provide multiple referrals, we will select only one out of these and nullify the remaining referrals. By doing this, researchers attempt to reduce the chances of bias in the sampling technique.