SL CT Chapter 11: Sampling and Data Notes

Sampling Error

Occurs when a characteristic of a sample differs from the population. The error is random and will occur even for samples which are well chosen.

Coverage Error

Occurs when a sample does not truly reflect the population. Avoided by having a large and unbiased sample.

Non-response Error

Occurs when a large number of people do not respond.

Measurement Error

Inaccuracies in measurement at the data collection stage.

Simple Random Sampling

Drawing names, random number generators, etc.

Systematic Sampling

Selecting members of the population at regular intervals

Convenience Sampling

Selecting members because they are easier to access.

Stratified and Quota Sampling

Useful when the population can be divided into subgroups. You divide into subgroups and choose from each group to get an even result.

Categorical Data

Describes a quality or characteristic.

Discrete

Take exact number values (usually from counting)

Continuous

Can take any numerical value from a certain range (usually from measuring)