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Graphing Least-Squares Regression Lines (best-fit lines) - Instructions.

|Clear Data. To clear all data from a list:  Press STAT.  Hit ENTER to select the EDIT menu. Then move the cursor up ONTO the name of the list (L1).  |

|Press CLEAR and then ENTER. |

| |

|To clear an individual entry:  Select the value and press DEL. |

|Step 1.  Enter the data into the lists.  |[pic] |

|Locate and press the STAT button on the calculator.  Choose EDIT.  Simply type| |

|your data and press ENTER. Use your arrow keys to move between lists. | |

| | |

|NOTE: L1 is the x variable, L2 is the y variable | |

|Step 2.  Create a scatter plot of the data.  |

|     Go to STATPLOT (2nd Y=) and choose the first plot.  Turn the plot ON, set the icon to Scatter Plot (the first one), set Xlist to L1 and Ylist to L2 |

|and select a Mark of your choice. |

| |

|Note: to select something you must hit ENTER. |

| |

| |

|       To go back to the main screen, hit Quit (2nd MODE) |

|Step 3.  Choose Linear Regression Model. |[pic] |

|     Press STAT, arrow right to CALC, and arrow down to 4: LinReg (ax+b).  |The linear regression equation is |

|Hit ENTER.  When LinReg appears on the home screen, type the parameters L1, |y = 25.3x + 353.2 |

|L2, Y1.  The Y1 will put the equation into Y= for you. Then hit ENTER. |*(use this step for #1)* |

|(Y1 comes from VARS → YVARS, #Function, Y1) | |

|[pic]      [pic] | |

|Step 4.  Graph the Linear Regression Equation from Y1 with the scatter plot.|[pic] |

|     ZOOM #9 ZoomStat to see the graph. | |

|*(use this step for #1)* | |

|Step 5.  Is this model a "good fit"? |Step 6.  Finding values that are not in the data set. |

|     The correlation coefficient, r = .9336055153 which places the |If given x: Go to 2nd Calc (trace), select 1:value, enter in the x-value you |

|correlation into the "strong" category.  (0.7 or greater is a "strong" |are using, and hit Enter. The calculator will give you the answer. |

|correlation, 0.3 or below is a “weak” correlation.) |If given y: Go to y =, enter the given y-value in Y2, hit Graph, go to 2nd |

| |Calc (trace), select 5:intersect, and hit Enter 3 times. The calculator will |

|Yes, it is a "good fit". |give you the answer. |

|*(Use this step for #2)* |*(Use this step for #3 & 4)* |

Practice - Population and Licensed Drivers

The table below compares the population of a state to the number of licensed drivers in 1995.

1) Graph the data along with its

line of best fit on your calculator.

What is the equation for your line

of best fit (population is x and

drivers is y)?

2) Describe the correlation.

3) Find the number of licensed drivers in Massachusetts, given that it had a population of 6.1 million people in 1995. Go to CALC (2nd TRACE). Then select 1:value, enter the

x-value given (6.1), and hit enter. Write the answer below.

4) Find the population of a state that has 15.5 million licensed drivers in it. GO to the Y = and enter the y-value given (15.5) into Y2 =. Next go to the CALC (2nd TRACE) to find the intersection (5:) of the two lines. Hit ENTER 3 times. Write the answer below.

NOTE: The other way to find answers for #3 and 4 is to plug the value given

into its corresponding variable and solve the equation by hand.

5) Now draw your scatter plot. Make

sure to include the best fit line.

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