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Download as PDF; Printable version; ... = sample mean of differences = hypothesized population mean difference = standard deviation ...
Random variables are usually written in upper case Roman letters, such as or and so on. Random variables, in this context, usually refer to something in words, such as "the height of a subject" for a continuous variable, or "the number of cars in the school car park" for a discrete variable, or "the colour of the next bicycle" for a categorical variable.
The arithmetic mean of a population, or population mean, is often denoted μ. [2] The sample mean x ¯ {\displaystyle {\bar {x}}} (the arithmetic mean of a sample of values drawn from the population) makes a good estimator of the population mean, as its expected value is equal to the population mean (that is, it is an unbiased estimator ).
For example, let the design effect, for estimating the population mean based on some sampling design, be 2. If the sample size is 1,000, then the effective sample size will be 500. It means that the variance of the weighted mean based on 1,000 samples will be the same as that of a simple mean based on 500 samples obtained using a simple random ...
{{Historical populations}} is used as an information box on pages showing each census year with a population and a percent gain/loss comparison. It is intended to combine the functionalities of two existing templates, Template:US Census population and Template:Histpop, the former of which is specialized for the United States, and the latter of which lacks many features of the former.
In statistics, Welch's t-test, or unequal variances t-test, is a two-sample location test which is used to test the (null) hypothesis that two populations have equal means. It is named for its creator, Bernard Lewis Welch , and is an adaptation of Student's t -test , [ 1 ] and is more reliable when the two samples have unequal variances and ...
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In statistics and econometrics, cross-sectional data is a type of data collected by observing many subjects (such as individuals, firms, countries, or regions) at a single point or period of time.