11 - Scatterplot: A plot that displays the relationship...

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Scatterplot: A plot that displays the relationship between two quantitative variables measured on the same individuals. If one of the variables is an explanatory variable, it should be represented on the horizontal axis (x axis). Correlation: Measure of the strength and direction of the linear association between two quantitative variables x and y. Positive association: Two variables are positively associated when above-average values of one tend to accompany above-average values of the other and below-average values also tend to occur together. Negative association: Two variables are negatively associated when above-average values of one tend to accompany below-average values of the other and vice-versa. 1. Correlation makes no distinction between explanatory and response variables. It makes no difference which variable you call x and which you call y in calculating the correlation. 2. Because r uses the standardized values of the observations, r does not change when we change the units of measurement of x, y, or both. Measuring height in inches rather than
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