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1. Dr. Najma Baseer
MBBS, MHPE, PhD
Associate Professor Anatomy
IBMS KMU

2.  Any sampling method where some elements of population have no chance of
selection
 or where the probability of selection can't be accurately determined.
 Nonprobability Sampling includes:
1. Convenience sample
2. Quota Sampling
3. Purposive Sampling.
4. Snowball sampling
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3.  Used in exploratory research, where sample is selected
because they are convenient and are readily accessible to
the researcher
 The researcher using such a sample cannot scientifically
make generalizations about the total population from this
sample because it would not be representative enough.
 Suited for piloting
 You chose who you think should be in the study

4.  A common nonprobability method.
 The sample is selected based upon judgment.
 an extension of convenience sampling
 When using this method, the researcher must be
confident that the chosen sample is truly representative
of the entire population.
 Any study with a defined inclusion exclusion criteria
requires purposive/judgment sampling

5.  Quota sampling is the nonprobability equivalent of stratified
sampling.
 First identify the stratums and their proportions as they
are represented in the population
 Then convenience or purposive sampling is used to select
the required number of subjects from each stratum.

6.  Snowball sampling is a special nonprobability method used
when the desired sample characteristic is rare.
 It may be extremely difficult or cost prohibitive to locate
respondents in these situations.
 This technique relies on referrals from initial subjects to
generate additional subjects.
 It lowers search costs; however, it introduces bias because the
technique itself reduces the likelihood that the sample will
represent a good cross section from the population.