Lecture 3.1: Surveys Flashcards
Random (Probability) Sampling
- Everyone in the sampling frame has an equal
probability of being chosen - Important to achieve a representative sample
Non-Random (Non-Probability) Sampling
- Easier and convenient
- Unlikely to be representative
Simple Random Sampling
Each population member given an identifier and numbers selected at random
Stratified Sampling
Divide population into strata (subgroups) and select sample from each using simple random sampling
Cluster Sampling
Use natural ‘clusters’ in the population e.g. schools
Study all individuals within clusters
Systematic Sampling (not truly random!)
Every Nth population member selected
What is Validity?
How well a test measures what it is purported to
measure (the capacity of a test to give a true result)
What is Repeatability?
The degree to which a measurement made on one occasion agrees with the same measurement on a subsequent occasion
What is Selection Bias?
Error due to systematic differences in the
characteristics of the groups being studied due to
differences in the way they were selected
What is Information (Measurement) Bias?
Error due to systematic differences in the measurement or classification of individuals in the groups being studied
What is Instrument Bias?
- A type of Information (Measurement) Bias
- Systematic error due to inadequate design,
calibration or maintenance of instruments
What is Inter-Observer Bias?
- A type of Information (Measurement) Bias
- Systematic error between measurements of
different interviewers e.g. due to training
What is Precision?
- If lots of variation (random error), precision is
poor, if little random variation, measurement is
precise
What is Accuracy?
How close the average result is to the true value, poor accuracy is systematic error (bias)
