6.7
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6.7 Scatter Plots
description
6.7. Scatter Plots. 6.7 – Scatter Plots. Goals / “I can…” Write an equation for a trend line and use it to make predictions Write the equation for a line of best fit and use it to make predictions. 6.7 – Scatter Plots. - PowerPoint PPT Presentation
Transcript of 6.7
6.7
Scatter Plots
6.7 – Scatter Plots
Goals / “I can…”Write an equation for a trend line and use it to
make predictionsWrite the equation for a line of best fit and use it
to make predictions
6.7 – Scatter Plots
A scatter plot is a collection of data that explains a situation. We can enter a scatter plot onto our calculator.
An effective way to see a relationship in data is to display the information as a __________________.
It shows how two variables relate to each other by showing how closely the data points _______ to a line.
The following table presents information on tornado occurrences.Make a scatter plot for the table.
Year 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995
# of Tornadoes
201 593 616 897 654 919 866 684 1133 1234
scatter plot
fit
Year 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995
# of Tornadoes
201 593 616 897 654 919 866 684 1133 1234
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Do you notice a trend?
Scatter plots provide a convenient way to determine whether a ___________ exists between two variables.correlation
A __________ correlation occurs when both variables increase.
positive
A ___________ correlation occurs when one variable increases and the other variable decreases.
negative
If the data points are randomly scattered there is _______ or no correlation.little
Positive correlatio
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Negative correlati
on
little or no
correlation
Example 1: The scatter plots of data relate characteristics of children from
0 to 18 years old.
Match each scatter plot with the appropriate variables studied.1. age and height2. age and eye color3. age and time needed to run a certain distance
no correlation between age and eye color
as your age increases your height also increases
as your age increases the time
will decrease2 1 3
Sometimes points on a scatter plot are represented by a trend line or a _______________________.
You can study the line to see how the data behaves. You may have a basis predict what the data might be for values not given.
line of best fit
Example 2: Find the line of best fit for the scatter plot you made on the first page. To fit the line to the points, choose your line so that it best matches the overall trend. The line does not have to pass through any of the points.
6.7 – Scatter Plots
A trend line is the line that appears to explain the data. Where is a good line to fit the data you graphed?
Our calculator will find the line that explains the data the best. It is called the Line of Best Fit. (Regression Line)
Use the line of best fit to predict how many tornadoes may be reported in the United States in 2015 if the trend continues.
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If the trend continues we predict that there will be 1200 tornadoes reported in 2015.
6.7 – Scatter Plots
Steps to find line of best fit.1. Make sure you have put your numbers
into lists (STAT >> EDIT)2. Press STAT3. Press CALC4. Press 4 - LineReg5. Make sure the lists are L1 and L26. Press Enter
6.7 – Scatter Plots
Your screen should have A=B=r=
r is the Correlation Coefficient. This number explains how good of a fit is the data. If the number is close to 1 or –1 then the line of fit is really good.
If the data points are close to the line of best fit, it is said to have a ___________correlation.
strong
weak positive
weak negative
strong negative
strong positive
6.7 – Scatter Plots
Example:Find the line of best fit for the given
data.
Year 1995 1996 1997 1998 1999 2000 2001 2002 2003
Profit $5.5 $6.0 $6.4 $7.0 $7.4 $7.7 $8.4 $9.5 $9.5
