Sample size determination

sample sizeSampling sizessamplenumber of shotssample sizessizeestimating sample sizesestimating sufficient sample sizesfinite sampleonly 22 Bulldogs
Sample size determination is the act of choosing the number of observations or replicates to include in a statistical sample.wikipedia
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Power (statistics)

statistical powerpowerpowerful
In practice, the sample size used in a study is usually determined based on the cost, time, or convenience of collecting the data, and the need for it to offer sufficient statistical power.
Power analysis can be used to calculate the minimum sample size required so that one can be reasonably likely to detect an effect of a given size.

Confidence interval

confidence intervalsconfidence levelconfidence
For example, if a proportion is being estimated, one may wish to have the 95% confidence interval be less than 0.06 units wide.
A major factor determining the length of a confidence interval is the size of the sample used in the estimation procedure, for example, the number of people taking part in a survey.

Accuracy and precision

accuracyprecisionaccurate
Larger sample sizes generally lead to increased precision when estimating unknown parameters.
For example, if an experiment contains a systematic error, then increasing the sample size generally increases precision but does not improve accuracy.

Statistical hypothesis testing

hypothesis testingstatistical teststatistical tests
Such considerations can be used for the purpose of sample size determination prior to the collection of data.

Estimation theory

parameter estimationestimationestimated
Larger sample sizes generally lead to increased precision when estimating unknown parameters.
:where m is the sample maximum and k is the sample size, sampling without replacement.

Replication (statistics)

replicationreplicatereplicates
Sample size determination is the act of choosing the number of observations or replicates to include in a statistical sample.

Survey sampling

surveyssampleSample Survey
In complicated studies there may be several different sample sizes: for example, in a stratified survey there would be different sizes for each stratum.

Stratified sampling

stratificationstratifiedstratified random sampling
In complicated studies there may be several different sample sizes: for example, in a stratified survey there would be different sizes for each stratum.
For an efficient way to partition sampling resources among groups that vary in their means, variance and costs, see "optimum allocation".

Estimator

estimatorsestimateestimates
The estimator of a proportion is, where X is the number of 'positive' observations (e.g. the number of people out of the n sampled people who are at least 65 years old).
A consistent sequence of estimators is a sequence of estimators that converge in probability to the quantity being estimated as the index (usually the sample size) grows without bound.

Proportionality (mathematics)

proportionalinversely proportionalproportion
The estimator of a proportion is, where X is the number of 'positive' observations (e.g. the number of people out of the n sampled people who are at least 65 years old). A relatively simple situation is estimation of a proportion.

Central limit theorem

Lyapunov's central limit theoremlimit theoremscentral limit
Several fundamental facts of mathematical statistics describe this phenomenon, including the law of large numbers and the central limit theorem.

Standard error

SEstandard errorsstandard error of the mean
When estimating the population mean using an independent and identically distributed (iid) sample of size n, where each data value has variance σ 2, the standard error of the sample mean is:

Sample (statistics)

samplesamplesstatistical sample
Sample size determination is the act of choosing the number of observations or replicates to include in a statistical sample.

Effect size

Cohen's deffect sizesmagnitude
Cohen's d is frequently used in estimating sample sizes for statistical testing.

Standard deviation

standard deviationssample standard deviationSD
This so-called range rule is useful in sample size estimation, as the range of possible values is easier to estimate than the standard deviation.

Opinion poll

opinion pollingpollapproval rating
These numbers are quoted often in news reports of opinion polls and other sample surveys.

Stepwise regression

Backward eliminationforward selectionStepwise
For additional consideration, when planning an experiment, computer simulation, or scientific survey to collect data for this model, one must keep in mind the number of parameters, P, to estimate and adjust the sample size accordingly.

Thematic analysis

A tool akin to a quantitative power calculation, based on the negative binomial distribution, has been suggested for thematic analysis.
For example, Fugard and Potts offered a prospective, quantitative tool to support thinking on sample size by analogy to quantitative sample size estimation methods.

Degrees of freedom (statistics)

degrees of freedomdegree of freedomEffective degrees of freedom
All the parameters in the equation are in fact the degrees of freedom of the number of their concepts, and hence, their numbers are subtracted by 1 before insertion into the equation.

Statistical inference

inferential statisticsinferenceinferences
The sample size is an important feature of any empirical study in which the goal is to make inferences about a population from a sample.

Statistical population

populationsubpopulationsubpopulations
The sample size is an important feature of any empirical study in which the goal is to make inferences about a population from a sample.

Census

UK censuscensusespopulation census
In a census, data is sought for an entire population, hence the intended sample size is equal to the population.