In a scatterplot, a straight line is typically produced when there is a linear relationship between two quantitative variables. Specifically, if you have:
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Independent Variable (Predictor): This is the variable that you manipulate or use to predict another variable. It’s often plotted on the x-axis.
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Dependent Variable (Response): This is the variable that you measure or observe to see how it changes in response to the independent variable. It’s typically plotted on the y-axis.
Examples of pairs of quantitative variables that can show a straight line in a scatterplot include:
- Height and Weight: Assuming a specific population, height could predict weight, showing a linear correlation.
- Study Hours and Exam Scores: More study hours may correlate with higher exam scores, demonstrating a linear relationship.
For the scatterplot to exhibit a straight line, the relationship between these variables should be consistent, meaning that as the independent variable increases, the dependent variable typically increases (or decreases) at a constant rate. This results in a linear trend.