Maths AI terms: Q

Q

QuadrantHL only · also quadrants, first quadrant, second quadrant, third quadrant, fourth quadrant, CAST diagram

One of the four regions into which the $x$- and $y$-axes divide the coordinate plane, numbered 1 to 4 anticlockwise starting from the region where both coordinates are positive.

Introduced in 3.8 The unit circle and trigonometric equations

Quadratic equationalso quadratic equations, quadratic

A polynomial equation of degree 2, which can be written as $ax^2 + bx + c = 0$ with $a \ne 0$.

Introduced in 1.8 Equations and systems using technology

Quadratic formulaHL only · also formula for quadratic equations, quadratic equation formula

The formula $x = \dfrac{-b \pm \sqrt{b^2 - 4ac}}{2a}$

Quadratic modelalso quadratic function, quadratic models

A model of the form $f(x) = ax^2 + bx + c$, where $a$, $b$

Quadratic regressionHL only · also quadratic regression curve, QuadReg

Fitting a model of the form $y = ax^2 + bx + c$ to bivariate data by least squares.

Introduced in 4.13 Non-linear regression

Qualitative dataalso categorical data, categorical variable, qualitative variable

Data that describe a quality or category, such as colour, nationality or a yes/no answer, rather than a numerical amount.

Introduced in 4.1 Collecting data and sampling

Quantitative dataalso numerical data, quantitative variable

Data that are numerical values of a quantity that can be counted or measured, so that calculations such as a mean are meaningful.

Introduced in 4.1 Collecting data and sampling

QuestionnaireHL only · also questionnaires, survey design

A set of written questions, given in the same form to every respondent, used to collect data from the members of a sample.

Introduced in 4.12 Data collection and reliability

Quota samplingalso quota sample, quotas

A method in which a fixed number of members is required from each category of the population, and members are chosen by the data collector, not at random, until each category's number is reached.

Introduced in 4.1 Collecting data and sampling

Quotient law of logarithmsHL only · also quotient law, log of a quotient, quotient rule for logarithms

For $a, x, y > 0$ with $a \ne 1$, $\log_a\left(\frac{x}{y}\right) = \log_a x - \log_a y$

Quotient ruleHL only · also quotient formula, u over v rule

The rule for differentiating a quotient of two functions: if $y = \frac{u}{v}$, where $u$ and $v$ are functions of $x$