Announcements

1
Announcements

• Homework 3 and Homework 4 grades and solutions
  were already posted on Carmen.osu.edu website.
• Homework 5 (4.2, 4.6, 4.12, 4.24, 4.32, 4.40,
  4.50, 4.60 in Chapter 4 ) is due Wednesday
  (10/17).
• Exam 1 is on Friday (10/19) in lecture.
• Exam 1 covers Chapters 1-4 and 6
• Bring a calculator (on cell phone or PDA
  calculators allowed), bring your ID, and one 8.5
  X 11 sheet of notes (both sides)
• Review for exam 1 on Thursday (10/18) in
  recitation.

2
Problem solving---Chapter 4

• 4.5 The U.S. Department of Transportation
  reported the number of speeding-related crash
  fatalities for the 20 dates that had the highest
  number of these fatalities between 1994 and 2003
  (Traffic Safety Facts, July 2005).
• a. By looking at the histogram of this data set,
  which one (mean or median ?) do you think has a
  larger value?
• b. Compute the mean and median number of
  speeding-related fatalities for these 20 days.
  Which one do you think is more representative of
  the sample and why?
• c. Explain why it is not reasonable to generalize
  from this sample of 20 days to the other 345 days
  of the year.

3
Problem solving---Chapter 4

• 4.10 Consider the following statement More
  than 65 of the residents of Los Angeles earn
  less than the average wage for that city. Could
  this statement be correct? If so, how? If not,
  why not?

4
Problem solving---Chapter 4

• 4.11 A sample consisting of four pieces of
  luggage was selected form among those checked at
  an airline counter, yielding the following data
  on xweight (in pounds)
• X1 33.5, X2 27.3, X336.7, X430.5
• Suppose that one more piece is selected denote
  its weight by X5. Find a value of X5 such that
  sample mean sample median.

5
Problem solving---Chapter 4

• 4.35 Blood cocaine concentration (in milligrams
  per liter) was determined for both a sample of
  individuals who had died from cocaine-induced
  excited delirium and a sample of those who had
  died from a cocaine overdose without excited
  delirium. The accompanying data are consistent
  with summary values given in the paper Fatal
  Excited Delirium Following Cocaine Use (Journal
  of Forensic Sciences 1997 25-31)

6
Questions for 4.35

• a. Determine the mean, median, quartiles and
  interquartile range for each of the two samples.
• b. Compute the standard deviation for these two
  sample, which sample has more variability?
• c. Are there any outliers in either sample? Any
  extreme outliers?
• d. Construct a comparative boxplot, and use it as
  a basis for comparing and contrasting the two
  samples. (Hint median marker, variability,
  whiskers etc.)

7
Problem solving---Chapter 4

• 4.41 A student took two national aptitude tests.
  The national average and standard deviation were
  475 and 100, respectively, for the first test and
  30 and 8, respectively, for the second test. The
  student scored 625 on the first test and 45 on
  the second test. Use Z scores to determine on
  which exam the student performed better relative
  to the other test takers.

8
Problem solving---Chapter 4

• 4.42 Suppose that your younger sister is
  applying for entrance to college and has taken
  the SATs. She scored at the 83rd percentile on
  the verbal section of the test and at the 94th
  percentile on the math section of the test.
  Because you have been studying statistics, she
  asks you for an interpretation of these values.
  What would you tell her?