A1 4.4 Notes

Scatter Plots and Line of Best FIt

​Objective: to interpret scatter plots, identify correlations between data sets,  and make predictions using data 

 

Scatter Plot is

A scatterplot is a graph that shows the relationship between two data sets. The two data sets are graphed as ordered pairs in a coordinate plane. 

Scatterplots can be used to show trend data

​The scatter plot shows the amounts x (in grams) of sugar and the number y of calories in 10 smoothies

1. How many calories are in the smoothie that contains 56 grams of sugar?

• 
  

2. How many grams of sugar are in a smoothie that contains 320 calories? 

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3. What tends to happen to the number of calories as the number of sugar increases?

Three Types of Correlation

• Positive

• Negative

• No correlation

​Correlation is the relationship between data sets. We can use scatter plots to describe the correlation between data.

Multiple Choice

What type of correlation does this scatter plot show?

• positive

• negative

• no correlation

• nonlinear association

Multiple Choice

What type of correlation does this graph have?

• positive

• negative

• none

• all of the above

Multiple Choice

What type of correlation does this graph have?

• Negative

• no association

• positive

Multiple Choice

What type of correlation does this scatterplot have?

• Positive association

• Negative association

• No association

​Ex. 3 Make a scatter plot of the data. Tell whether the data shows a positive, a negative, or no correlation.

Line of Best Fit

A line of best fit is a line drawn on a scatter plot that is close to most of the data points 

To use: 

1. Make a scatter plot of the data

2. Decide whether the data can be modeled  by a line 

3. Draw a line that appears to fit the data closely. There should be points above and below the line. 

4. Write the equation of the line. The points do not have to represent actual data pairs, but they must lie on the line of best fit

Multiple Choice

Which of the following lines represents the line of best fit for the scatter plot?

• A

• B

• C

• D

Multiple Choice

Which line is the best line of best fit?

• a

• b

• c

• i don't see any lines

Multiple Choice

What is a line of best fit used for?

• To make predictions

• To make the graph look pretty

• To connect the points

• To make it look like you know what you are doing

Multiple Choice

A small theme park is trying to determine the number of guests they should expect on a weekend, based on the temperature outside.  Based on the trend line, about how many guests should be expected if the temperature is around 80°?

• 8,300

• 8

• 7,300

• 9,300

Multiple Choice

The scatter plot shows the relationship between the number of chapters and the total number of pages for several books.  Use the trend line to predict how many chapters would be in a book with 180 pages. 

• 12 chapters

• 15 chapters

• 18 chapters

• 21 chapters