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Construct and interpret scatter plots and use trend lines to make predictions.
Learn step-by-step with practice exercises built right in.
A scatter plot shows the relationship between two sets of numerical data. Each point represents one data pair.
| Pattern | Type | Example |
|---|---|---|
| Points go up | Positive correlation | Height and weight |
| Points go down | Negative correlation | TV time and grades |
| No pattern | No correlation | Shoe size and IQ |
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A trend line is a straight line that best represents the data in a scatter plot.
Properties:
Use the trend line equation to predict values:
If the trend line is and :
For categorical data, use two-way tables to find relationships:
| Likes Math | Doesn't Like Math | Total | |
|---|---|---|---|
| Grade 7 | 30 | 20 | 50 |
| Grade 8 | 35 | 15 | 50 |
| Total | 65 | 35 | 100 |
Caution: Correlation does NOT mean causation! Just because two variables are related doesn't mean one causes the other.