MATH220 Elementary Statistics
Test 3
Due: Wednesday, July 1, 2020
Answer all of the following question. You are encouraged to use software; however, your answers must
provide the information necessary to illustrate your reasoning. Include screenshots (neatly edited).
This test assesses material covered in chapters 10 – 12.
1. The table below lists the number of manatee deaths related to encounters with watercraft and natural
causes for each of several different years.
a. Find the value of the linear correlation coefficient and determine whether there is a significant
linear correlation between the two variables.
b. Find the equation of the regression line. Let the number of natural deaths represent the response
(y) variable. What is the best predicted number of natural deaths in a year with 50 deaths from
encounters with watercraft?
2. Many people believe that fatal driving-while-intoxicated (DWI) crashes occur because of casual
drinkers who tend to binge on Friday and Saturday nights, whereas others believe that fatal DWI
crashes are caused by people who drink every day of the week. In a study of fatal car crashes, 216
cases are randomly selected from the pool in which the driver was found to have a blood alcohol
content over 0.10. These cases are broken down according to the day of the week, with the results
listed in the accompanying table. At the 0.05 significance level, test the claim that such fatal crashes
occur on the different days of the week with equal frequency. Does the evidence support the theory
that fatal DWI car crashes are due to casual drinkers or that they are caused by those who drink daily?
3. Samples of head breadths were obtained by measuring skulls of Egyptian males from three different
epochs, and the measurements are listed below (based on data from Ancient Races of the Thebaid, by
Thomson and Randall-Maciver). Changes in head shape over time suggest that interbreeding occurred
with immigrant populations. Use a 0.05 significance level to test the claim that the different epochs do
not all have the same mean. What do you conclude?
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