Name:                                                             :
Group (circle one): 1 = like broccoli, 2 = tolerate broccoli, 3 = dislike broccoli

 
Intro-Stat, Math 203, Candy bar Quiz 2
  1. The scatter plot below shows X = the number of powerboat registrations (in thousands, so X = 151 means 151,000 powerboats were registered) and Y = the number of manatees killed. The data points cover the years from 1977 to 1990 (in the state of Florida). Use the plot to answer the following questions. All questions can be answered from just the plot.


  1. The plot shows a fairly strong association between X and Y. Is this association positive or negative? How can you tell?

    2.  

     





     

  2. Make a rough guess at the correlation, r, between X and Y. Do not attempt to compute r, simply guess a value to one decimal place of accuracy, that is, which of the values, 1, 0.9, 0.8, … , -0.8, -0.9, -1 would you guess is the correlation? Explain.

    3.  

     






     

  3. Draw in what you consider to be a good linear regression line. According to your line, how many manatees would be killed if 400,000 powerboats were registered?

    4.  

     









     

  4. One of the observations, namely (559, 34) is plotted as a circle (the rest are plotted as diamonds). Residuals are defined as true value minus predicted value. Estimate the residual for the circular data point (and your drawn in line).