1. Module 4
Math 075

2. 1.1 Types of Statistical Studies

3. Observational Study
Observational study (Imply association): Observes individuals (population) and measures variables of interest.

4. Good Research Question: Population
Criteria:
The population
The variable: What is being measured
A numerical characteristic about the population related to the variable.

5. Let’s Practice: Teachers The average amount of time spent grading
What is the average amount of time teachers spend outside of the school grading papers?
What is the population?
What is the is being measured?
What is the numerical characteristic about the population related to the variable?
Teachers
Amount of time spent grading
The average amount of time spent grading

6. Let’s Practice
What is the average amount of time spent on social media?
What is the population?
What is the is being measured?
What is the numerical characteristic about the population related to the variable?
A population was not identified
Time spent on social media
The average amount of time spent on social media

7. Population Vs. Sample
We’d like to know about an entire population of individuals, but examining all of them is usually impractical, if not impossible.
We settle for examining a smaller group of individuals—a sample—selected from the population.

8. Population Vs. Sample
Sampling is a natural thing to do. Think about sampling something you are cooking—you taste (examine) a small part of what you’re cooking to get an idea about the dish as a whole.

9. Checking for Understanding
The age of every third person entering a clothing store.
The amount of energy collected from every wind turbine on a wind farm.
The annual salary of each pharmacist at a pharmacy.

10. Checking for Understanding
The cholesterol level of 20 patients in a hospital with 100 patients.
The soil contamination levels at 10 locations near a landfill.
The revenue of each of the 30 companies in the Dow Jones Industrial Average.

11. Confounding/Lurking Variables
Found in Observational Studies
Outside factors that effect the outcome of the study.

12. Confounding Variable
A study of child care enrolled 1364 infants and followed them through their sixth grade year in school. Later, the researcher published an article in which they stated that “the more time children spent in child care from birth to age four-and-a-half, the more adults tended to rate them, both at age four-and-a-half and kindergarten, as less likely to get along with others, as more assertive, as disobedient, and as aggressive.
Home-life
Disposition
What they area exposed to growing up

13. Confounding Variable
One study of cell phones and the risk of brain cancer looked at a group of 469 people who have brain cancer. The investigators matched each cancer patient with a person of the same age, gender, and race who did not have brain cancer, then asked about the use of cell phones. Results “Our data suggest that the use of handheld cellular phones is not associated with the risk of brain cancer.”
Environmental factors other than cell phones.

14. Summarize Population Confounding Variables Implies: One Variable
Linked
Relationship
Correlated
Associated
Connected
One Variable

15. Experiment
Experiment(Imply Causation) : Intentionally manipulates one variable (explanatory) in an attempt to cause and effect on another variable (response). The purpose to create a cause-and-effect relationship.

16. Variables Explanatory: The variable that is being manipulated
Response: The variable we are measuring

17. Explanatory and Response
Does reducing screen brightness increase battery life in laptop computers? To find out, researchers obtained 30 new laptops of the same brand. They chose 15 of the computers at random and adjusted their screens to the brightest setting. The other 15 laptops screens were left at the default setting-moderate brightness. Researches then measure how long each machine’s battery lasted. Justify your answer.
Explanatory: Screen brightness
Response: The length of each battery lasted

18. Explanatory and Response
An educator wants to compare the effectiveness of computer software for teaching biology with that of a textbook presentation. She gives a biology pretest to each of a group of high school juniors, then randomly divides them into two groups. One group uses the computer, and the other studies the text. At the end of the year, she tests all students again and compares the increase in biology test scores in the two groups. Justify your answer.
Explanatory: Delivery method
Response: The grades on the post test

19. Summarize Experiment Cause and Effect Implies: Two Variables
Increase
Lower
Effect
Two Variables
One variable is being manipulated

20. Association and Causation
1) Explain the joke in this cartoon. 2) Write another example of the joke.

21. Association When two variables are related
Turn and Talk: Describe how these two variables are related. Can you think of another example? Be prepared to share out.

22. Causation When one variable causes another variable to change. A  B
Example: As you run faster, the number of calories you are burning increases.
Think-Pair-Share: Other examples???

23. Speed Dating
You will have two minutes to find a partner and discuss the first question and write down any notes that you need.
We will repeat until all questions are answered.  

24. Observational Study Vs. Experiment
Observational study (Imply association): Observes individuals (population) and measures variables of interest.
Experiment(Imply Causation) : Intentionally manipulates one variable (explanatory) in an attempt to cause and effect on another variable (response). The purpose to create a cause-and-effect relationship.

25. Observational Study or Experiment
Does reducing screen brightness increase battery life in laptop computers? To find out, researchers obtained 30 new laptops of the same brand. They chose 15 of the computers at random and adjusted their screens to the brightest setting. The other 15 laptops screens were left at the default setting-moderate brightness. Researches then measure how long each machine’s battery lasted. Is this an observational study or experiment? Justify your answer.
Experiment because the treatment was imposed on the laptops.

26. Observational Study or Experiment
An educator wants to compare the effectiveness of computer software for teaching biology with that of a textbook presentation. She gives a biology pretest to each of a group of high school juniors, then randomly divides them into two groups. One group uses the computer, and the other studies the text. At the end of the year, she tests all students again and compares the increase in biology test scores in the two groups. . Is this an observational study or experiment? Justify your answer.
Experiment because students were assigned randomly to the different teaching methods

27. Observational Study or Experiment
One study of cell phones and the risk of brain cancer looked at a group of 469 people who have brain cancer. The investigators matched each cancer patient with a person of the same age, gender, and race who did not have brain cancer, then asked about the use of cell phones. Results “Our data suggest that the use of handheld cellular phones is not associated with the risk of brain cancer.” Is this an observational study or experiment? Justify your answer.
Observational because the researchers did not assign people to either use or not use cell phones.

28. Observational Study or Experiment
A study of child care enrolled 1364 infants and followed them through their sixth grade year in school. Later, the researcher published an article in which they stated that “the more time children spent in child care from birth to age four-and-a-half, the more adults tended to rate them, both at age four-and-a-half and kindergarten, as less likely to get along with others, as more assertive, as disobedient, and as aggressive. Is this an observational study or experiment? Justify your answer.
Observational because children weren’t assigned to different amounts of child care.

29. Exit Ticket What is the difference between a sample and population?
What is the difference between an Observational Study and Experiment?
What are the three criteria for a good research question.
Choose one.