A scatter plot shows whether two variables move together. Before drawing one, it helps to know its ranges (for the axes), the strength of the relationship (r) and the trend line.
How to use the Scatter Plot Calculator
- Enter the x values.
- Enter the matching y values in the same order.
- Read the summary and trend line.
Results update as you type, and everything is calculated in your browser.
How it works
Means and ranges set up the axes; the correlation coefficient measures the linear relationship; the least squares line gives the trend.
Tips
- Sketch the points first – a quick drawing shows whether a slope should be positive or negative.
- Keep the order of the points consistent in every formula.
- Vertical lines have an undefined slope; horizontal lines have slope zero.
- Use the same units on both axes when you measure distances or angles.
Common mistakes to avoid
- Swapping x and y coordinates.
- Subtracting the coordinates in a different order in the numerator and denominator of the slope.
- Forgetting that the distance is always positive.
Inputs explained
| Field | What to enter |
|---|---|
| x values | A list of numbers separated by commas, spaces or new lines |
| y values (same order) | A list of numbers separated by commas, spaces or new lines |
What each result means
- Correlation coefficient r = corr([x values], [y values (same order)])
- Number of points = min(count([x values]), count([y values (same order)]))
- Mean of x = mean([x values])
- Mean of y = mean([y values (same order)])
- Range of x = max([x values]) – min([x values])
- Range of y = max([y values (same order)]) – min([y values (same order)])
- Trend line slope = slope([x values], [y values (same order)])
- Trend line intercept = intercept([x values], [y values (same order)])
Formula
r = Σ(x − x̄)(y − ȳ) ÷ √[Σ(x − x̄)² Σ(y − ȳ)²], ŷ = a·x + bWorked example
Inputs — x values: 160, 165, 170, 175, 180, 185; y values (same order): 55, 60, 64, 70, 74, 80.
Results — Correlation coefficient r = 0.998511; Number of points = 6; Mean of x = 172.5; Mean of y = 67.166667; Range of x = 25; Range of y = 25; Trend line slope = 0.988571; Trend line intercept = -103.361905; Strength of the linear relationship = Strong.
Key terms
- Correlation
- The strength and direction of a linear relationship.
Frequently asked questions
What does a scatter plot show?
The relationship between two quantitative variables, one point per observation.
What does r close to 0 mean?
No linear relationship – though there may be a curved one.
What is an outlier?
A point far from the overall pattern; it can change r a lot.
Should I always add a trend line?
Only when the relationship looks roughly linear.
What formula does the Scatter Plot Calculator use?
r = Σ(x − x̄)(y − ȳ) ÷ √[Σ(x − x̄)² Σ(y − ȳ)²], ŷ = a·x + b.