Lesson #72 Writing the equation of a line of best fit (day 2)
Do Now: The following scatter plot shows the prices and weights of several pieces of her jewelry,
as well as a trend line that shows their relationship.
Directions: Find the equation of the line of best fit
using the points (1, 50) and (8, 400).
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a) Explain what the slope means in terms of the scenario above.
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b) Explain what the y-intercept means in terms of the scenario above.
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1. The following scatter plot shows a plumber’s charges (not including parts) and the time he
spends at each job, as well as a trend line that shows their relationship.
a) Find the equation of the line of best fit.
Label the two points chosen in your work.
b) Interpret the slope: __________________________________________________________
c) Interpret the y-intercept: ______________________________________________________
2. A student in Mr. Dagger’s 8th grade class asked 9 of her friends how far they live from school.
She then asked her friends how long it takes them, on average, to get from home to school. The
student plotted the data points in the following scatter plot.
a) Draw a line of best fit on the student’s scatter plot
using (10, 25) and (15, 35).
Explain why your trend line is accurate.
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b) Find the equation of this line of best fit.
c) Explain what the y-intercept means in terms of the scenario.
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d) Explain what the slope means in terms of the scenario.
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e)
Use the line of best fit equation to predict the time (in min) when the distance is 8 miles.
f)
Use the trend line equation to determine the distance (in mi) when the time is 13 minutes.
3a) Make a scatter plot using the data below and draw in the line of best fit using the points
(52, 50) and (62, 90).
Temperature
(F)
52
56
Number of
Cricket Chirps
per Minute
50
78
62
72
90
115
b) Determine the equation of the line of best fit.
c) Explain the y-intercept in your equation above in the context of this situation. Is it a reasonable
y-intercept?
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4. Carl graphed the data shown in the scatter plot below and then drew a trend line.
Using the words positive or negative and linear or
non-linear, describe the type of correlation shown in
the scatter plot to the right.
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Why is a trend line not a good fit for this data?
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