chapter 7

form

(of an association) The form of an association can be linear or non-linear. The form can contain cluster of data. A residual plot can help determine if a particular form is appropriate for modeling the relationship.

strength

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. See slope.

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.

circle graph

A way of displaying data that can be put into categories (like what color you prefer, your gender, or the state you were born in). A circle graph shows the proportion each category is of the whole.

central angle

An angle with its vertex at the center of a circle.

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.

association

A relationship between two (or more) variables. An association between numerical variables can be displayed on a scatterplot, and described by its form, direction, strength, and outliers. Possible association between two categorical variables can be studied in a relative frequency table. Also see scatterplot.

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.

positive association

If one variable in a relationship increases as the other variable increases, the direction is said to be a positive association.

simple interest

Interest paid on the principal alone.

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.