What is the symbol ≙
most commonly used for in a mathematical or math-related context?
- LaTeX produces the symbol with
\hateq
. - The symbol has Unicode codepoint
U+2259
. - The respective Unicode code chart shows it with the name
ESTIMATES
and the annotation= corresponds to
. Note that the names and annotations there are often not helpful, incomplete, or even misleading. - Entering it into the English Wikipedia currently redirects to the article Correspondence (mathematics).
Where and how is ≙
used in math or related fields? (By "related" I am thinking of statistics and physics.)
I believe to remember that I have seen it in some sort of "correspondence" meaning in a college-level science class.
Best Answer
The hat above the equals sign is an estimator. Originaly estimators are used on terms. For example:
$$\widehat{\theta}(X)$$
But it has appeared (sometimes) more convenient to use it with an equals sign, especially in statistics. It has transformed a substantive (θ is an estimator for . . .) into a verb.
x ≙ . . .
then reads asx estimates . . .
You use it instead of a plain equals sign when you do not have a strict equality between the left term and the right expression. Statistically speaking, it symbolizes an estimation of an unobservable quantity.