chapter 7

strength(of an associaition)

A description of how much scatter there is in the data away from the line or curve of best fit.

negative slope

A line has negative slope if it slopes downward from left to right on a graph.

positive slope

A line has positive slope if it slopes upward from left to right on a graph.

line of best fit

A line of best fit shows a trend in the data representing where the data falls. This line does not need to touch any of the actual data points. Instead, it shows where the data generally falls. The line is a mathematical model of the data.

outlier

A number in a set of data that is much larger or much smaller than the other numbers in the set.

central angle

An angle with its vertex at the center of a circle

linear equation

An equation in two variables whose graph is a line. For example, y = 2.1x − 8 is a linear equation. The standard form for a linear equation is ax + by = c, where a, b, and c are constants and a and b are not both zero. Most linear equations can be written in y = mx + b form, which is more useful for determining the line's slope and y-intercept.

form

the form of an association can be linear of a non-linear :the form can contain cluster of data

slope

A ratio that describes how steep (or flat) a line is. Slope can be positive, negative, or even zero, but a straight line has only one slope. Slope is the ratio pic or pic, sometimes written pic. When the equation of a line is written in y = mx + b form, m is the slope of the line. Some texts refer to slope as the ratio of the "rise over the run." A line has positive slope if it slopes upward from left to right on a graph, negative slope if it slopes downward from left to right, zero slope if it is horizontal, and undefined slope if it is vertical. lope is interpreted in context as the amount of change in the y-variable for an increase of one unit in the x-variable.

frequency table

A table that displays counts, or frequencies, of data.

negative association

If one variable decreases as the other variable increases, there is said to be a negative association.

y-intercept

The point(s) where a graph intersects the y-axis. A function has at most one y-intercept; a relation may have several. The y-intercept of a graph is important because it often represents the starting value of a quantity in a real-world situation. For example, on the graph of a tile pattern the y-intercept represents the number of tiles in Figure 0. We sometimes report the y-intercept of a graph with a coordinate pair, but since the x-coordinate is always zero, we often just give the y-coordinate of the y-intercept. For example, we might say that the y-intercept of the graph below is (0, 2), or we might just say that the y-intercept is 2. When a linear equation is written in y = mx + b form, b tells us the y-intercept of the graph. For example, the equation of the graph below is y = x + 2 and its y-intercept is 2.

lattice point

The points on a coordinate grid where the grid lines intersect. The diagram below shows two lattice points. The coordinates of lattice points are integers.

y=mx+b

When two quantities x and y have a linear relationship, that relationship can be represented with an equation in y = mx + b form. The constant m is the slope, and b is the y-intercept of the graph. For example, the graph below shows the line represented by the equation y = 2x + 3, which has a slope of 2 and a y-intercept of 3. This form of a linear equation is also called the slope-intercept form.

circle graph

a way of displaying data that can be put into categories: a circle graph shiws the proportion each category is of the whole

association

an organization of people with a common purpose and having a formal structure