Flashcards
Statistics-Population and Samples
Cards in this deck (15)
- 1PopulationA collection of all items
- 2Finite populationA population is one in which each individual member can be given a number. Therefore making it countable.
- 3Infinite populationA population might be so large that it is difficult or impossible to give each member a number –
e.g. grains of sand on the beach). - 4CensusInformation gathered from the whole population
- 5Sampling unitA single member of the population which could be included in a sample.
- 6Sampling frameA list of all sampling units, by name or number, from which samples are to be drawn.
- 7SampleA selection of sampling units from the sampling frame.
- 8Simple random sampleA simple random sample of size n, is one taken so that every possible sample of size n has an
equal chance of being selected.
The members of the sample are independent random variables, X1, X2 … - 9Sample surveyAn investigation using a sample
- 10StatisticA quantity calculated only from the data in the sample, using no unknown parameters (for
example, µ and σ). Calculated purely from the observations from a sample. - 11Sampling distribution of a statisticThis is the set of all possible values of the statistic together with their individual probabilities; this
is sometimes better described by giving the relevant probability density function. - 12Advantages of a census*Every member of the population is used.
*It is unbiased.
*It gives an accurate answer. - 13Disadvantages of a census*It takes a long time.
*It is costly.
*It is often difficult to ensure that the whole population is surveyed. - 14Advantages of a sample*It takes a long time.
*It is costly.
*It is often difficult to ensure that the whole population is surveyed - 15Disadvantages of a sample*Uncertainty, due to the natural variation – two samples are unlikely to give the same result.
*Uncertainty due to bias prevents the sample from giving a representative picture of the population.
*Sampling from an incomplete sampling frame.
*Preferences - e.g. interviewing only people without (fierce) dogs
NOTE: Bias cannot be removed by increasing the size of the sample.
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- Flashcards on Statistics-Population and Samples, created by Zara Kanani on 06/02/2018.
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- Zara Kanani
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