Scatter diagram
Topic: Economic Data: Census, NSS, Surveys and Statistical Tools · NCERT: Class 11, Ch 6 "Correlation"
Meaning
A scatter diagram is a graph that plots pairs of values of two variables as dots. One variable goes on the X-axis and the other on the Y-axis. The pattern of dots shows how the two variables are related: whether they move together or in opposite directions, and how closely. It gives no number. It is still useful because it also shows relationships that are not straight lines.
Example
Plot the years of schooling of farmers against their yield per acre. The dots drift upward from left to right, which shows positive correlation. Karl Pearson's coefficient for this data puts a number on it: r = 0.644.
Don't confuse with
- Karl Pearson's coefficient of correlation (r): r gives an exact number, but it only measures straight-line relationships. If Y = X² for X from −3 to 3, r = 0, yet the scatter diagram clearly shows a U-shaped curve.
Related concepts
- Measures of central tendency
- Arithmetic mean
- Weighted arithmetic mean
- Median
- Quartiles
- Decile
- Percentiles
- Mode
- Bimodal and multimodal distribution
- Modal class