Bivariate Data

Univariate vs. Bivariate Involves a single variable Dealing with describing the variable Information gathered is about the distribution (range or mean) Bivariate Involves two variables Dealing with causes or relationships Purpose is to explain Represented in a scatterplot

Scatterplot A type of diagram using Cartesian coordinates to display values for two variables for a set of data Data is displayed as a collection of points, each having the value of one variable determining the position on the horizontal axis and the value of the other variable determining the position on the vertical axis When looking at scatter plots, we will look for direction, form, strength and outliers

Direction A lot like slope Positive relationships If one variable increases the other variable increases If one variable decrease the other variable decreases Ex: As the temperature increases the amount of people at the beach will increase. As the temperature decreases the amount of people at the beach decreases.

Direction Negative relationships As one variable increases, the other variable decreases. Ex: As the amount of time you spend exercising increases, the less time it takes you to run a mile.

Direction It is possible to have no association or direction at all. It occurs when the scatter plot looks like a random splattering of dots.

Form Determines if there is a straight line (linear) relationship or curved A straight line relationship will appear as a cloud or swarm of points stretched out in a consistent straight form

Form Quadratic Exponential

Form Logarithmic

Strength Determines how strong a relationship between two variables is. At one extreme, the points appear to follow a straight stream At the other extreme, the points appear as a vague cloud with no pattern

Outliers Do not follow the pattern They may be in either the x-direction, y-direction or both directions

Variables Predictor variable Response variable Also called explanatory variable Variable that can be used to predict the value of another variable (independent variable) Response variable Variable that depends on the predictor variable (dependent variable) Predictor variables are independent of response variables For example: The amount of people at the beach depends on the temperature. Predictor variable: temperature Response variable: population at the beach