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[h] SL 4.1 Concepts of population and sample
[q] Population
[a] When recording data about a certain group of people, objects, etc, the population refers to every number of that group.
[q] Sample
[a] Refers to a subset of the whole population.
[q] Discrete Data
[a] When there are only a certian number of values possible,often counatable. For example: no.of siblings, shoe size, no.of pages, etc.
[q] Continuous Data
[a] Data that can take any value within a range, usually measured and approximated/rounded. For example: height, mass, time taken, etc.
[q] Reliability
[a] The reliability of a set can be compromised by: missing data, small sample size, or errors in handling data. An outlier could be an extreme data point or could have arisen due to an error.
[q] Sampling Methods
[a] When taking a sample, it should be random, to avoid bias. There are many methods of achieving this randomness: simple, convenience, systematic, quota and stratified.
[q] Simple
[a] A method such as drawing names from a hat.
[q] Population
[a] A method that is the most accessible for the sampler, such as asking the people in the room you are in, for some data.
[q] Systematic
[a] When you randomly select the first data point, then select the rest at regular intervals.
[q] Quota
[a] For example, if your population has certian percentages of genders, ages, races, etc, then your random sample would maintain those percentages.
[q] Stratified
[a] When you pick an equal number of data points from all of the subgroups of a population.
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