5-7 Scatter Plots

_______________ plots are graphs that relate two different sets of data by displaying them as ordered pairs. Usually scatter plots contain positive numbers so the data will be graphed in the quadrant. Scatter plots are used to find trends in data. Three types of relationships:

Scatter Plots

SCATTER

FIRST

When y tends to increase as x increases, the two sets of data have a

positive correlation

When y tends to decrease as x increases, the two sets of data have a

negative correlation

When x and y are not related , the two sets of data

have a no correlation

Make a scatter plot of the data in the table. What type of relationship does the scatter plot show?     

Make a Scatter Plot

Dollars Spent2 4 6 8 10 12 14

Gal

lon

s B

ough

t

1

3

2

Positive correlation

When two sets of data have a positive or negative correlation, you can use a ___________________ to show the correlation more clearly.

A trend line is a line on a scatter plot, drawn near the points, that shows a ______________.

You can use a trend line to ______________ a value between 2 known data values, which is called _______________

Or you can use a trend line to _______________ a value outside the range of known data values, which is called __________________

Trend Lines

TREND LINE

CORRELATION

ESTIMATEINTERPOLATION

PREDICTEXTRAPOLATION

Make a scatter plot of the datausing your graphing calculator.

Press STAT. Press Enter to edit your lists of data.

Enter the values of x-values (dollars spent) into L1. Enter them in order. Hit enter after putting in a value to move to the next value. Enter the values of y-values (gallons bought) into L2.

*To erase a list, push the UP arrow to highlight a list name. Press Clear and Enter to erase the whole list.

   

 

Using the Graphing Calculator

Make a scatter plot of the datausing your graphing calculator.

Press Y =. Clear any lines that are there. Press 2nd and y= to edit your STATPLOT. Press Enter.

Choose “On.” To turn your plot on. Xlist: should be L1. Ylist: Should be L2. Press Zoom and choose option 9: ZoomStat. You should see a scatter plot of the data.

What is the correlation?

   

 

Using the Graphing Calculator

Using the Graphing Calculator• A graphing calculator can compute the equation of the line of

best fit using a method called

• Find the Equation of a trend line: Press STAT> CALC> Option 4: LinReg(ax +b). Press Enter

Press 2nd and 1 to Choose L1. Press “,” and Press 2nd and 2 to choose list 2. Press VARS. Press over to Y-VARS. Press Enter, Enter.

Press Enter. Write the equation of the data:

LINEAR REGRESSION

.244 .123y x

Homework: p. 368-369 #’s 8-15, 19, 20