1. Announcements
100 Years: Let's celebrate! The National Park Service turns 100 on August 25, 2016, and everyone can take part in the celebration! To honor this day, let’s take a look at some vintage tourist experiences across the nation at our glorious National Parks.

24. Please stand for the pledge. 

25. 3.1 HW Key
There were 1,755 qualified applicants for the HISD’s magnet schools program. 53% were accepted, 17% were wait-listed, and the other 30% were turned away for lack of space.
7. a) Yes, it is reasonable to assume that heart and respiratory disease caused approximately 38% of U.S. deaths in 1999, since there is not possibility for overlap. Each person could only have one case of death.
b) Since the percentages listed add up to 73.7%, other causes must account for 26.3% of U.S. deaths.
c) A pie chart is a good choice (with the inclusion of the “Other” category), since causes of U.S. deaths represent parts of a whole. A bar chart would also be a good display.

26. 9. a) It is NOT reasonable to assume the 66% of those polled expressed a belief in either ghosts or astrology. The percentages in the table add up to 185%! This tells us that we are not dealing with parts of a whole and that some respondents believe in more than one of the psychic phenomena listed. In other words, belief in ghosts and belief in astrology are not mutually exclusive. There is no way to know what percent of respondents believe in ghosts or astrology.
b) As in 7a, since the percentages are not meant to add up to 100%, there is no way to determine what percentage of respondents did not believe in any of these phenomena. With data collected in this fashion, the only way to determine the percentage of people who did not believe in any of the psychic phenomena would be to add another category to the survey when collecting the data.
c) Since the percentages were not intended to add up to 100%, a pie chart is not appropriate. A bar chart nicely displays the percentages as relative heights of bars. Also, we are probably interested in the most popular phenomena, it makes sense to make a Pareto Chart, with the most common belief occurring in the first chart.

27. 11. The bar chart shows that grounding is the most frequent cause of oil spillage for these 50 spills, and allows the reader to rank the other types as well. If being able to differentiate between these close counts is required, use the bar chart. The pie chart is also acceptable as a display, but it’s difficult to tell whether, for example, there is a greater percentage of spills caused by grounding or hull failure. If you want to showcase the cause of oil spills as a fraction of all 50 spills, use the pie chart.

28. Contingency Tables

29. Contingency Tables
A contingency table allows us to look at two categorical variables together.
It shows how individuals are distributed along each variable, contingent on the value of the other variable.
Example: we can examine the class of ticket and whether a person survived the Titanic:

30. Contingency Tables (cont.)
The margins of the table, both on the right and on the bottom, give totals and the frequency distributions for each of the variables.
Each frequency distribution is called a marginal distribution of its respective variable.
The marginal distribution of Survival is:

31. Contingency Tables (cont.)

32. Contingency Tables (cont.)
Each cell of the table gives the count for a combination of values of the two values.
For example, the second cell in the crew column tells us that 673 crew members died when the Titanic sunk.

33. Conditional Distributions
A conditional distribution shows the distribution of one variable for just the individuals who satisfy some condition on another variable.
The following is the conditional distribution of ticket Class, conditional on having survived:

34. Conditional Distributions (cont.)
The following is the conditional distribution of ticket Class, conditional on having perished:

35. Conditional Distributions (cont.)
The conditional distributions tell us that there is a difference in class for those who survived and those who perished.
This is better shown with pie charts of the two distributions:

36. Conditional Distributions (cont.)
We see that the distribution of Class for the survivors is different from that of the nonsurvivors.
This leads us to believe that Class and Survival are associated, that they are not independent.
The variables would be considered independent when the distribution of one variable in a contingency table is the same for all categories of the other variable.

37. Segmented Bar Charts
A segmented bar chart displays the same information as a pie chart, but in the form of bars instead of circles.
Here is the segmented bar chart for ticket Class by Survival status:

38. Example
A company held a blood pressure screening clinic for its employees. The results are summarized in the table below by age group and blood pressure level.
Find the marginal distribution of blood pressure level.
Age BP
Under 30
30-49
Over 50
Low 27 38 31
Normal 48 90 92
High 23 59 72

39. Example
A company held a blood pressure screening clinic for its employees. The results are summarized in the table below by age group and blood pressure level.
Find the conditional distribution of blood pressure level for employees under 30.
Age BP
Under 30
30-49
Over 50
Low 27 38 31
Normal 48 90 92
High 23 59 72

40. Homework Assignment
Page 38: #18, 20 – 23
Review Ch.1 – 3 pages 2 – 32