Scatter Plot & Correlation
Plot paired data, compute r and r², and get the least-squares line with a plain-English read.
Correlation measures linear association only — always look at the plot too.
① Answer
② Steps
③ Why it works
The correlation coefficient r standardizes the co-movement of x and y into [−1, 1]: +1 is a perfect uphill line, −1 perfect downhill, 0 no linear pattern. R² is the fraction of y’s variation the line explains. But r is blind to curves and bullied by outliers — the scatter plot is the real diagnostic; the number just summarizes it.