Sampling Methods Flashcards
simple random sampling
Method: assign number then random number generator
Advantages: bias free, easy and cheap, equal chance of being chosen
Disadvantages: not suitable for big populations, sampling frame needed
systematic sampling
Method: chosen at regular intervals, kth elements
Advantages: simple and quick, large population
Disadvantages: suitable only if sample frame is there, introduces bias if not random
stratified sampling
Method: divided into groups, simple random then in groups, same proportion
Advantages: reflects population, proportional representation
Disadvantages: classified into strata is a must, sampling frame is needed
quota sampling
Method: divided based on characteristics, actively chose people to fill quota
Advantages: small sample representative, no sampling frame needed, quick, easy cheap
Disadvantages: bias, non-responses not recorded
opportunity sampling
Method: info from the people available
Advantages: easy and inexpensive
Disadvantages: not representative, dependent on researcher
population
whole set of items of interest
sample
subset of the population, representative
sample unit
sampled individuals
sample frame
units individually named to form a list
census
information from the entire population
Advantages: accurate
Disadvantages: time consuming, cannot be done when testing involves destruction
cluster sampling
sampling a few subgroups
self-selected sampling
open to be sampled
measure of central tendency
centre of data (mean, mode, median)
standard deviation
distance from the mean, spread of data
variance
standard deviation squared
outliers
extreme values, (1.5 x IQR) +/- UQ/LQ
causal relationship
variable directly causes change in the other, correlation does not mean causation
regression
creating a model to explain the data
interpolation
estimating inside the range
extrapolation
estimating outside the range
midrange
(lowest + highest) / 2
