Lesson 4.6Scatterplots and Lines of Fit

Scatterplots•A scatterplot is a graph in which two sets of data are plotted as ordered pairs in a coordinate plane.

•Scatterplots are used to investigate a relationship between two variables.

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GPA vs. Hours Studying Per Night

# Hours Studying per Night

Unw

eigh

ted

GPA

Scatterplots Cont. If the pattern is linear, you can draw a line to summarize the data. This can help you to identify the trend and strength of the correlation.

0 1 2 3 4 5 6012345

GPA vs. Hours Studying Per Night

# Hours Studying per Night

Unw

eigh

ted

GPA

Positive Correlation If the x-coordinates and the y-coordinates both increase, then it is POSITIVE CORRELATION. This means that both are going up, and they are related.

Positive Correlation If you look at the age of a child and the child’s height, you will find that as the child gets older, the child gets taller. Because both are going up, it is positive correlation.

Age 1 2 3 4 5 6 7 8Height “

25 31 34 36 40 41 47 55

Negative Correlation If the x-coordinates and the y-coordinates have one increasing and one decreasing, then it is NEGATIVE CORRELATION. This means that 1 is going up and 1 is going down, making a downhill graph. This means the two are related as opposites.

Negative Correlation If you look at the age of your family’s car and its value, you will find as the car gets older, the car is worth less. This is negative correlation.

Age of car(years)

1 2 3 4 5

Value $30,000 $27,000 $23,500 $18,700 $15,350

No Correlation If there seems to be no pattern, and the points looked scattered, then it is no correlation.

This means the two are not related.

No Correlation If you look at the size shoe a baseball player wears, and their batting average, you will find that the shoe size does not make the player better or worse, then are not related.

Real-World Determine whether the graph shows a positive correlation, a negative correlation, or no correlation. If there is a positive or negative correlations, describe its meaning in the situation.

Real-World Determine whether the graph shows a positive correlation, a negative correlation, or no correlation. If there is a positive or negative correlations, describe its meaning in the situation.

Best- Fit Line If the data points do not lie in a line, but they lie close to a line, we can draw a line of fit. We can find the equation of that line and use it to make predictions.

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cases

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