sampling

1. Types of Sampling
 Simple Random Sample
 Systematic
 Stratified Random Sample
 Cluster sampling
 Convenience
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Alliance
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2. Simple Random Sample
 Every subset of a specified size n from the
population has an equal chance of being selected
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Alliance
Project

3. Systematic Sample
 Every kth member ( for example: every 10th
person) is selected from a list of all population
members.
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Alliance
Project

4. Stratified Random Sample
 The population is divided into two or more groups
called strata, according to some criterion, such as
geographic location, grade level, age, or income,
and subsamples are randomly selected from each
strata.
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Alliance
Project

5. Cluster Sample
 The population is divided into subgroups (clusters)
like families. A simple random sample is taken of
the subgroups and then all members of the cluster
selected are surveyed.
Math
Alliance
Project

6. Convenience Sample
 Selection of whichever individuals are easiest to
reach
 It is done at the “convenience” of the researcher
Math
Alliance
Project

7. Errors in Sampling
 Non-Observation Errors
 Sampling error: naturally occurs
 Coverage error: people sampled do not match the
population of interest
 Underrepresentation
 Non-response: won’t or can’t participate
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Alliance
Project

8. Errors of Observation
 Interview error- interaction between interviewer
and person being surveyed
 Respondent error: respondents have difficult time
answering the question
 Measurement error: inaccurate responses when
person doesn’t understand question or poorly
worded question
 Errors in data collection
Math
Alliance
Project