1. Data Exploration
A random sample of 32 individuals from the 2000 US Census is shown to the left.
1.) How old is the youngest person in the sample? The oldest?
2.) About what percent of the sample is 65 or older?
3.) about what percent of the population is younger than 65? Justify your answer.
Example 2: (Individuals and variables)
In Super Bowl XXXVII, the Tampa Bay Buccaneers defeated the Oakland Raiders. Here is a portion of Tampa Bay’s team roster:
No. Pos. Ht. Wt. Birth date Exp. College
Brad Johnson QB /13/ Florida State
Warren Sapp DT /06/ Miami
Martin Gramatica K /27/ Kansas State
Tom Tupa P /06/66 14 Ohio
What individuals does this data set describe?
(b) How many variables does the data set contain? Identify each as categorical or quantitative.
(c) What do you think are the units for each of the quantitative variables?

2. Data Exploration
A random sample of 32 individuals from the 2000 US Census is shown to the left.
1.) How old is the youngest person in the sample? The oldest?
2.) About what percent of the sample is 65 or older?
3.) about what percent of the population is younger than 65? Justify your answer.
Example 4 (Individuals and variables)
In Super Bowl XXXVII, the Tampa Bay Buccaneers defeated the Oakland Raiders. Here is a portion of Tampa Bay’s team roster:
No. Pos. Ht. Wt. Birth date Exp. College
Brad Johnson QB /13/ Florida State
Warren Sapp DT /06/ Miami
Martin Gramatica K /27/ Kansas State
Tom Tupa P /06/66 14 Ohio
(a) What individuals does this data set describe? Ans: Players on the Tampa Bay Buccaneers football team
(b) How many variables does the data set contain? Identify each as categorical or quantitative. Ans: 7; height, weight, and experience are quantitative; jersey number, position, birth date, and college are categorical
(c) What do you think are the units for each of the quantitative variables? Ans: height (inches), weight (pounds), experience (years)

3. 1.1 Day 2: Where do data come from?
More with Experiments and Observational Studies

4. A statistical study begins with a question of interest.
Do not rely on personal experiences or one case snapshots for inference. Rely on carefully produced data
The most important fact about any statistical study is how the data were produced
Ways to gather data:
1.) observational study
2.) experimental study

5. Observational Study
Sometimes all you can do is watch, and eventually patterns seem to emerge
Definition: observes individuals and measures variables of interest but does not attempt to influence the responses
A sample survey is an example
Limitations: you can not conclude cause and effect from observational studies

6. Experiment
Deliberately impose some treatment on individuals in order to observe their responses
Actively impose some treatment in order to observe the response
Can conclude cause and effect

7. Example 1 The political gender gap
There may be a “gender gap” in political party preference in the United States, with women more likely than men to prefer Democratic candidates. A political scientist interviews a large sample of registered voters, both men and women. She asks each voter whether they voted for the Democratic or the Republican candidate in the last congressional election. Is this study an experiment? Why or why not? What variables does the study measure?
Ans: No, this is an observational study. The political scientist is simply interviewing people and recording their responses to a question, not imposing a treatment and trying to measure their responses to the treatment. Sex and political party preference are the two variables that were measured. Note that both are categorical variables.

8. Example 2 Does welfare work?
To see if a required jobs program will help mothers escape welfare, such a program must actually be tried. Choose two similar groups of mothers when they apply for welfare. Require one group to participate in a job-training program, but do not offer the program to the other group. Comparing the income and work record of the two groups after several years will show whether requiring training has the desired effect. Is this study an experiment? Why or why not? What variables does the study measure?

9. Do cell phones cause cancer?
iRespond Question
Multiple Choice F
E4196E09-C635-FC4B-BBD2-3418AE44C512
A.) yes
B.) no
C.) I'm not sure
D.)
E.)

10. Statistics in the news

12. To do list
Using the iPads, complete the activity in pairs: “Where do Data Come From”
Turn in the activity & work on 1.1 SUMMARY worksheet from yesterday
Log in to Quizlet and practice the vocabulary