Rohan Chorge2013033
— A sample is “a smaller (but
hopefully representative) collection of units from a population used to
determine truths about that populationWhy sample?
— Resources (time, money) and workload
— Gives results with known accuracy
that can be calculated mathematically
— The sampling frame is the list from
which the potential respondents are drawn
— Registrar’s office
— Class rosters
— Must assess sampling frame errors
— What is your population of interest?
— To whom do you want to generalize
your results?
— All doctors
— School children
— Indians
— Women aged 15-45 years
— Other
— Can you sample the entire
population?
— 3 factors that influence sample
representative-ness
— Sampling procedure
— Sample size
— Participation (response)
— When might you sample the entire
population?
— When your population is very small
— When you have extensive resources
— When you don’t expect a very high
response
— Probability (Random) Samples
— Simple random sample
— Systematic random sample
— Stratified random sample
— Multistage sample
— Multiphase sample
— Cluster sample
— Non-Probability Samples
— Convenience sample
— Purposive sample
— Quota
SAMPLING FRAME
— In the most straightforward case,
such as the sentencing of a batch of material from production (acceptance
sampling by lots), it is possible to identify and measure every single item in
the population and to include any one of them in our sample. However, in the
more general case this is not possible. There is no way to identify all rats in
the set of all rats. Where voting is not compulsory, there is no way to identify
which people will actually vote at a forthcoming election (in advance of the
election)
— As a remedy, we seek a sampling
frame which has the property that we can identify every single element and
include any in our sample .
— The sampling frame must be
representative of the population
PROBABLITY SAMPLING
— Probability sampling includes:
— Simple Random Sampling,
— Systematic Sampling,
— Stratified Random Sampling,
— Cluster Sampling
— Multistage Sampling.
— Multiphase sampling
