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Examining Relationships Between Variables . Journal Topic . A medical study finds that short women are more likely to have heart attacks that women of average height, while tall women have the fewest heart attacks. Does this mean that being short causes heart attacks?
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Journal Topic A medical study finds that short women are more likely to have heart attacks that women of average height, while tall women have the fewest heart attacks. Does this mean that being short causes heart attacks? What other variables would have to be considered?
When comparing Variables it is important to understand that… • The relationship between two variables can be strongly influenced by other variables that are lurking in the background.
When you examine the relationships between two or more variables, first ask the familiar key questions about the data • Who: are the individuals being described • What: are the variables? • Why were the data gathered? • When, where, how, and by who were the data produced?
When comparing two variables there are two possible outcomes • 1. Is there a simple relationship between the two? • 2. Does one variable cause change in the other?
Response vs. Explanatory • Response Variables – measures the outcome of a study. • Explanatory Variable – helps explain or influence changes in a response variable. • How does this relate to independent and dependent variables?
Identify the Explanatory and Response Variables • Alcohol has many effects on the body. One effect is a drop in body temperature. To study this effect, researchers give several different amounts of alcohol to mice, then measure the change in each mouse’s body temperature in the 15 minutes after taking the alcohol. • What is the explanatory and response variable?
Identify the Explanatory and Response Variables • Jim wants to know how the mean 2005 SAT math and Verbal scores in the 50 states are related to each other. He doesn’t think that either score explains or causes the other. Jim has two related variables and neither is an variable. • Julie looks at some data. She asks, “Can I predict a state’s mean 2005 SAT Math score if I know its mean 2005 SAT Verbal Score?” Julie is treating the Verbal score as the variable and the Math score as the variable.
Think – Pair – Share • Individually, write down an example of a situation similar to the ones we just completed as a class. In one of your examples, a response variable should cause a change in the explanatory variable. The second example should be simply exploring the relationship between the two.
For each of the following situations, is it more reasonable to simply explore the relationship between the two variables or to view one of the variables as an explanatory variable and the other as a response variable? In the later case, which is the explanatory variable?
1. The amount of time a student spends studying for a statistics exam and the grade on the exam. 2. The weight in kilograms and height in centimeters of a person. 3. Inches of rain in the growing season and the yield of corn in bushels per acre. 4. A student’s grade in statistics and in French 5. A family’s income and the years of education their eldest child completes.
