# The Best

Learning to do Linear Regressions
Exploring Data on the TI-84

The average height in inches of United States children from ages 7 to 15 is given:
Age (yrs.) |7 |8 |9 |10 |11 |12 |13 |14 |15 | |Height (in.) |46.97 |48.43 |52.00 |53.98 |55.98 |57.99 |60.00 |62.01 |63.86 | |to enter the data STAT, 1:Edit, enter data into L1 and L2

1. to set up the plot of the data 2nd ,STAT PLOT, 1:PLOT1, ENTER

On

Type: scatter
Xlist:   L1
Ylist:   L2
Mark   (any)

2. to graph the scatter plot ZOOM , 9: ZoomStat

3. to turn on correlation coefficient CATALOG   DiagnosticON ENTER

4. to find the linear regression STAT, CALC,   4:LinReg(ax+b) L1, L2, y1
and paste it into the y1 (found under VARS,Y-VARS,1:Function, 1:Y1)
equation on the home screen

Analysis:
1. What is the slope of the line?   (Round answer 3 places behind decimal and include units.) In a complete sentence, explain the real-world meaning of this slope. (In discussion round to nearest whole number.)
2. What is the y-intercept?   (Round answer 3 places behind decimal and include units.)   In a complete sentence, explain the real world meaning for the y intercept.   (In discussion round to nearest whole number.) Is this reasonable?
3. What is a reasonable domain and range? Explain why you chose these and include units.
4. Interpolate to find the average height of a 9½-year-old child.   (Express answer in feet and inches.) Is it feasible to use this model to find this answer?   Explain.
5. Extrapolate to find the height of a 25 year old.   (Express answer in feet and inches rounding to the nearest ½ inch.) Is it feasible to use this model to find this answer?   Explain.
6. Use the model to determine the average age of a child (in years and months) who is 55 in. tall.   Is it feasible to use this model to find this answer?   Explain.
7. Discuss the correlation coefficient and if...