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Market Research---Sampling (Sample Size (requires a larger sample size,…
Market Research---Sampling
Quota Sampling
The aim is to obtain a sample that is "representative" of the overall population.
First:
The population is divided by the most important variables such as income, age and location.
Then:
The required quota sample is then drawn from each stratum.
Advantages
Quick and easy way of obtaining a sample
Disadvantages
Not random, so some risk of bias
Need to understand the population to be able to identify the basis of stratification
Judgement Sampling
A deliberate choice of a sample - the opposite of random
Advantages
Good for providing illustrative examples or case studies
Disadvantages
Samples often small
Cannot extrapolate from sample
Very prone to bias
Systematic sampling
After randomly selecting a starting point from the population between 1 and *n, every nth unit is selected.
Advantages
Ensures sample is spread across the population
Easier to extract the sample than via simple random
Disadvantages
Can be costly and time-consuming if the sample is not conveniently located
Simply Random Sampling
This makes sure that every member of the population has an equal chance of selection.
Advantages
Simple to design and interpret
Can calculate both estimate of the population and sampling error
Disadvantages
Need a complete and accurate population listing
May not be practical if the sample requires lots of small visits over the country
Cluster Sampling
Units in the population can often be found in certain geographic groups or "clusters" .
A random sample of clusters is taken, then all units within the cluster are examined.
Advantages
Good for face-to-face surveys
Quick and easy
Doesn't need complete population information
Disadvantages
Expensive if the clusters are large
Greater risk of sampling error
Convenience Sampling
Uses those who are willing to volunteer and easiest to involve in the study.
Advantages
Subjects are readily available
Large amounts of information can be gathered quickly
Disadvantages
Prone to volunteer bias
The sample is not representative of the entire population, so results can't speak for them - inferences are limited.
Definition
Sampling is an effective way of obtaining opinions from a wide range of people, selected from a specific group, in a bid to find out more about a whole group in general.
Simple Design
Method of selection
Plans for analysing and interpreting the results.
Sample structure
Sample Size
requires a larger sample size
overall confidence level
Always have margin of error
Depends on