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U+2252 ≒ APPROXIMATELY EQUAL TO OR THE IMAGE OF: Which is used like "≈" or "≃" in Japan, Taiwan, and Korea. U+2253 ≓ IMAGE OF OR APPROXIMATELY EQUAL TO: A reversed variation of U+2252 ≒ APPROXIMATELY EQUAL TO OR THE IMAGE OF. U+225F ≟ QUESTIONED EQUAL TO: U+2A85 ⪅ LESS-THAN OR APPROXIMATE: U+2A86 ⪆ GREATER-THAN OR APPROXIMATE
Greek letters (e.g. θ, β) are commonly used to denote unknown parameters (population parameters). [3]A tilde (~) denotes "has the probability distribution of". Placing a hat, or caret (also known as a circumflex), over a true parameter denotes an estimator of it, e.g., ^ is an estimator for .
In statistics, the 68–95–99.7 rule, also known as the empirical rule, and sometimes abbreviated 3sr, is a shorthand used to remember the percentage of values that lie within an interval estimate in a normal distribution: approximately 68%, 95%, and 99.7% of the values lie within one, two, and three standard deviations of the mean, respectively.
In mathematical formulas, the ± symbol may be used to indicate a symbol that may be replaced by either of the plus and minus signs, + or −, allowing the formula to represent two values or two equations.
The table shown on the right can be used in a two-sample t-test to estimate the sample sizes of an experimental group and a control group that are of equal size, that is, the total number of individuals in the trial is twice that of the number given, and the desired significance level is 0.05. [4] The parameters used are:
[14] [15] It may also mean "similar to", [16] including "of the same order of magnitude as", [13] such as "x ~ y" meaning that x and y are of the same order of magnitude. Another approximation symbol is the double tilde ≈, meaning "approximately/almost equal to".
A mathematical coincidence often involves an integer, and the surprising feature is the fact that a real number arising in some context is considered by some standard as a "close" approximation to a small integer or to a multiple or power of ten, or more generally, to a rational number with a small denominator.
The arithmetic mean of a population, or population mean, is often denoted μ. [2] The sample mean ¯ (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).