Investigate influential observations while keeping correlation separate from causation.
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First lesson in this subject: Read data before calculating
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Each dot pairs an x value with a y value. The four pairs (1, 2), (2, 4), (3, 6), (4, 8) rise together exactly along a line. Their correlation is positive.
Correlation summarizes linear association, not a cause. Even a perfect rising line cannot by itself show that changing x causes y to change. A shared cause or the way the data were collected could explain the association.
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First lesson in this subject: Read data before calculating
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Practice · Uncover a hidden line by removing planted anomalies from a scatterplot.
Book · Read distributions, question samples, and explore how groups and outliers change a conclusion.
Previous lesson · Combine totals correctly and see how changing group proportions can reverse a comparison.
Next lesson · Use random assignments to understand how surprising a difference is.
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