PSY1022 Lecture 7: PSY1022 – lecture – Week 7
26 May 2018
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PSY1022 – lecture – Week 7
- representative sample
• findings needs to be generalisable
• a simple is representative if the characteristics of the same approximate
that of the population
• if they do not - the population is said be a biased sample
- effect of sample size
• smaller samples tend to deviate more from the population mean than
larger samples - more uncertainty
- statistical inference
• refers to the process by which we derive generalisations about
populations on the basis on sample data
• key to statistical inference - sampling theory
•
o refers to the techniques we use to draw representative samples
from populations
o two basic categories
o
▪ probability sampling methods
▪
▪ methods in which the odds - probability of
selectively a particular individual are known - each
individual has an equal chance of being selected and
the selection process is random
▪ non-probability methods
▪
▪ methods in which the odds of selecting a particular
individual are not known, each individual does not
have an equal change of being selected and the
selection process is not random
o techniques - probability sampling methods
o
▪ simple random sampling - with replacement
▪
▪ where the probability of selecting each individual is
known and does not change as each selection is
made
▪ use random number table to make selections
▪ simple random sampling - without replacement
▪
▪ where the probability of selecting each individual is
known, but changes as each selection is made
▪ systematic random sampling
▪
▪ where everyone in the population is listened and
every nth individual on the list is selected
▪ a random number table is used to determine the
starting point and n= population size divided by
desired sample size.
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