Section 4.1 Exploring Associations between Two Quantitative Variables?

Example: Is there, on a national scale, an association between TV watching and obesity? What do you think? What does the data Show?

Data: Country TV Viewing Hours Obesity Rate Australia Austria Belgium Canada Denmark Finland Ireland Italy Japan Korea New Zealand Portugal Spain Sweden Switzerland Turkey United Kingdom322.9 United States The average hours of TV watched by adults in 18 industrialized countries and the Obesity rate of adults in those countries. Does there seem to be a associated? Lets look at a bar graph and see if that helps.

Data:

New Tool: Scatter Plot: To build a scatter plot treat your explanatory variable as x, and your response variable as y, and plot your data on an (x, y) plane. Height Weight Jim68145 Jill65130 Frank71173 Mark73205 Eric66143 Zach70166

New Tool: Scatter Plot: We look at three things on a scatter Plot: Is there a linear association? What is the direction? How strong is the association?

Correlation. Correlation is a numerical value that summarizes the direction and strength of the association between two quantitative variables. Properties: Denoted r. Positive r indicated a positive association Negative r indicated a negative association Values fall within the interval [-1, 1] The closer to r = zero the weaker the association.

Correlation Would you expect a positive association, a negative association or no association between the age of the car and the mileage on the odometer? a)Positive association b)Negative association c)No association

New Tool: Scatter Plot: What would we expect as the r value for the scatter plot below?

Questions

Calculating Correlation. Height Weight Jim68145 Jill65130 Frank71173 Mark73205 Eric66143 Zach70166

Remember the TV thing: Country TV Viewing Hours Obesity Rate Australia Austria Belgium Canada Denmark Finland Ireland Italy Japan Korea New Zealand Portugal Spain Sweden Switzerland Turkey United Kingdom322.9 United States r =

Remember the TV thing: Country TV Viewing Hours Obesity Rate Australia Austria Belgium Canada Denmark Finland Ireland Italy Japan Korea New Zealand Portugal Spain Sweden Switzerland Turkey United Kingdom322.9 United States r =

Questions