Procedure: Get a small string that is anywhere from 13 to 15 centimeters in length.
Measure the length of your string and record the measurement in the table below.
Put one knot in the string, measure the length of the string, and record the length in
the table below. (Remember that the more precise you are with your measurements
the better this will work) You don’t need to stretch your string super tight but
stretch it straight.
Length of String (in
1. Graph the data by hand by placing x’s on the graph below. Make sure you
label and scale your x and y-axis.
2. What is the y intercept for the data?_____________ What does the y-intercept
represent in this case?
3. What type of mathematical model does the data appear to fit?
4. Draw a line through the y-intercept and through as many other points as
5. Find the slope of the line you drew by picking two points on the line.
6. Write a sentence interpreting the slope in this situation.
7. Use the slope and y intercept to write the equation of the line.
8. Post your equation in the discussion and compare yours to another
classmate. Are they the same? If so, why? If not, why not?
9. Now input your data into a spreadsheet and make a scatter-plot. Add a trend
line to the data(in statistics it is called a line of best fit or regression line).
10. What is the slope?____________________ What is the y-intercept?____________________
11. Write the equation of the line using the slope and y-intercept from #10.
12. How does your equation using the spreadsheet’s regression compare with
the equation you wrote when you drew the line by hand? Explain.
Use your equation you got from the spreadsheet to complete the following
13. Graphically, the y-intercept is where the graph intersects the y-axis. It can be
found by letting x=0. Use the equation to find the y-intercept.
14. Graphically, the x-intercept is where the graph crosses the x-axis. It can be
found by letting y=0. Use the equation to find the x-intercept.
15. Interpret the meaning of the x-intercept for the string problem.
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