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Section 3.1 Day 1 Scatterplots and Correlation. Learning Targets. After this section, you should be able to… IDENTIFY explanatory and response variables CONSTRUCT scatterplots to display relationships INTERPRET scatterplots. Scatterplots and Correlation. Explanatory and Response Variables
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Section 3.1 Day 1Scatterplots and Correlation Learning Targets After this section, you should be able to… • IDENTIFY explanatory and response variables • CONSTRUCT scatterplots to display relationships • INTERPRET scatterplots
Scatterplots and Correlation • Explanatory and Response Variables Ex: The number of hours spent on Facebook and GP A response variable: An explanatory variable: *** NOTE**** sometimes it does not matter which variable is which and there is no clear explanatory and response variable
Scatterplots and Correlation • Ex: Explanatory and Response? Identify the explanatory and response variables in each setting. 1). A sociologist looks at data on debt for college graduates, their current income and how stressed they feel. 2). An investigation to determine a relationship between height and weight.
Scatterplots and Correlation • Displaying Relationships: Scatterplots The most useful graph for displaying the relationship between two quantitative variables is a scatterplot. • A scatterplotshows the relationship between _____ quantitative variables measured on the ______ individuals. • The ____________ variable appears on the horizontal axis • The ____________variable appears on the vertical axis. • Each individual in the data appears as a _____ on the graph. How to Make a Scatterplot • Decide which variable should go on each axis. • Remember, the eXplanatory variable goes on the X-axis! • Label and scale your axes. • Plot individual data values.
Scatterplots and Correlation • Displaying Relationships: Scatterplots Make a scatterplot of the relationship between body weight and pack weight. Since Body weight is our eXplanatory variable, be sure to place it on the X-axis!
Scatterplots and Correlation • Scatterplot on Graphing Calculator • Enter data in lists • Go to StatPlot (2nd y=) • Turn plot on, select scatterplot, enter lists • Press Zoom and 9:ZoomStat • AP Tip: Label your graph!! Including proper labels is more important than graphing each point precisely.
Scatterplots and Correlation • Interpreting Scatterplots “DOFS” • Direction positive or negative association • Form linear, quadratic, exponential, etc, • Strength strong, weak, moderately strong/weak • Outliers, clusters, gaps
Ex: Interpret the Scatterplot Gestation (days) vs. mean life expectancy (years) of common animals • Describe the association in context. • What form does the relationship take? • How strong is the relationship? • Are there any outliers?
CYU pg. 149 1-5 • 1). The association is positive. The longer the eruption, the longer the wait between eruptions. One reason for this may be because if it erupts longer, it takes more energy to build up enough for the next eruption. • 2). The form is roughly liner with two clusters, one short eruption, one longer eruption. • 3). The relationship is fairly strong. The points seem to be fairly close to one another. • 4). There appear to be some outliers around each cluster, but not many are far away from the majority of data points. • 5). The Starnes family needs to know how long the last eruption lasted in order to predict how long until the next one.
