Statistical Sciences 1023A/B Study Guide - Midterm Guide: Esophageal Cancer, Nicotine Patch, Randomized Experiment

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Published on 19 Apr 2013
School
Western University
Department
Statistical Sciences
Course
Statistical Sciences 1023A/B
Professor
Stats 1023B Notes
Unit 1: Benefits and Risks of Using Statistics
Chapter 1: Introduction to Statistics
1.1 Statistics
- A collection of procedures and principles for gaining and analyzing information in order to
help people make decisions when faced with uncertainty.
- Heat or hypothalamus case study: left vs. right, survival nature of tendencies
- newborn infants are soothed by the sound of the normal adult heartbeat
1.2 Detecting Patterns and Relationships
- Hypothesis: men have lower pulsing rate than women
- To conduct a statistical study properly, one must
1. Get a representative sample.
Those chosen: sample, whole group: population
Researchers constrained to “convenience samples”
2. Get a large enough sample.
The more diverse or variable the individuals, the larger the sample necessary
3. Decide whether the study should be an observational study or a randomized experiment.
When we are merely observing things about our sample, it’s an observational study
Randomized experiment: people randomly assigned to one of two groups
Placebo pills to not influence people with expectations
Aspirin prevents heart attacks study: aspirin does indeed prevents h.a.’s 55% as likely
1.3 Don’t be deceived by improper use of statistics
George Bush vs. Chrysler president, bullshit since only 200 respondents and biased
New Jersey release of air toxins: based on overall not pounds per square mile
Causal vs. correlation: Smoking MAY lower kids’ IQ
Marijuana smokers: observational study, since they cannot be randomly assigned
Cheating on test couple, exonerated since it was cultural reason why they both got question
wrong
1.4 Summary and Conclusions, Exercises
Relationships do not always mean cause and effect
Exercises 3, 8, 9, 13, 15 (pp 10 - 12)
4. Explain why the number of people in a sample is an important factor to consider when
designing a study.
If groups are highly variable we need a larger group to create a mean
8. Suppose you have a choice of two grocery stores in your neighborhood. Because you hate
waiting, you want to choose the one for which there is generally a shorter wait in the checkout line. How
would you gather information to determine which one is faster? Would it be sufficient to visit each store
once and time how long you had to wait in line? Explain.
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Visit numerous times on different days and take an average
9. Suppose researchers want to know whether smoking cigars increases the risk of esophageal
cancer.
a. Could they conduct a randomized experiment to test this? Explain.
No because you can’t force people to smoke.
b. If they conducted an observational study and found that cigar smokers had a higher rate of
esophageal cancer than those who did not smoke cigars, could they conclude that smoking cigars
increases the risk of esophageal cancer? Explain why or why not.
No, because it’s observational and there may be other factors causing them to have esophageal
cancer.
13. Suppose you have 20 tomato plants and want to know if fertilizing them will help them
produce more fruit. You randomly assign 10 of them to receive fertilizer and the remaining 10 to receive
none. You otherwise treat the plants in an identical manner.
a. Explain whether this would be an observational study or a randomized experiment.
Randomized
b. If the fertilized plants produce 30% more fruit than the unfertilized plants, can you conclude
that the fertilizer caused the plants to produce more? Explain.
Yes
15. National polls are often conducted by asking the opinions of a few thousand adults
nationwide and using them to infer the opinions of all adults in the nation. Explain who is in the sample
and who is in the population for such polls.
Sample: those asked, population all adults
Chapter 2: Reading the News
The “Seven Critical Components”
1. The source of the research, and its funding
2. The researchers who had contact with the participants
3. The individuals or objects studied (i.e. the sample) and how they were selected
4. The exact nature of the measurements made or questions asked
5. The setting in which the measurements were taken
6. Differences between groups, in addition to the factor of interest
o Confounding variables
7. The extent or size of any claimed effect or differences
o Can be statistically significant, but have no practical significance
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Exercises 3a, 5, 7, 10, 12, 15 (pp 33 - 34)
3a. Prison administration study: do guards treat prisoners fairly: biased results: if guards asked
prisoners, unbiased if trained independent interviewers
5. Two pieces of data from Hypothetical News Article 1: major and GPA
7. Is it necessary data consists of numbers? No, like college major
10. Suppose a study were to find that twice as many users of nicotine patches quit smoking than
nonusers. Suppose you are a smoker trying to quit. Which version of an answer to each of the following
components would be more compelling evidence for you to try the nicotine patches? Explain.
a. Component 3. Version 1 is that the nicotine patch users were lung cancer patients, whereas the
nonusers were healthy. Version 2 is that participants were randomly assigned to use the patch or not
after answering an advertisement in the newspaper asking for volunteers who wanted to quit smoking.
Version 2
b. Component 7. Version 1 is that 25% of nonusers quit, whereas 50% of usersquit. Version 2 is that 1%
of nonusers quit, whereas 2% of users quit.
Version 1
12. Explain why news reports should give the extent or size of the claimed effects or differences from a
study instead of just reporting that an effect or difference was found.
A small statistical difference may not have any practical importance.
15. Moore (1991, p. 19) reports the following contradictory evidence: “The advice columnist Ann
Landers once asked her readers, ‘If you had it to do over again, would you have children? She received
nearly 10,000 responses, almost 70% saying ‘No!’. . . A professional nationwide random sample
commissioned by Newsday . . . polled 1373 parents and found that 91% would have children again.”
Using the most relevant one of the Seven Critical Components, explain the contradiction in the two sets
of answers.
Component 3: Volunteer respondents
Chapter 3 Measurements, Mistakes and Misunderstandings
What makes a good measurement?
1. Any measurement requires a definition
2. Any measurement is a process: unbiased and precise is best
- Natural variability
o Repeated measurements on a single unit
o Measurements from the same population
- Open ended(Faculty I’m in __) vs. closed ended (choose a faculty: science, health science, eng)
- Bias: in wording(buy vs obtain)
- With preference, people tend to comply (Do you agree that…)
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Document Summary

Unit 1: benefits and risks of using statistics. A collection of procedures and principles for gaining and analyzing information in order to help people make decisions when faced with uncertainty. Heat or hypothalamus case study: left vs. right, survival nature of tendencies. Newborn infants are soothed by the sound of the normal adult heartbeat. Hypothesis: men have lower pulsing rate than women. To conduct a statistical study properly, one must: get a representative sample. Researchers constrained to convenience samples : get a large enough sample. The more diverse or variable the individuals, the larger the sample necessary: decide whether the study should be an observational study or a randomized experiment. When we are merely observing things about our sample, it"s an observational study. Randomized experiment: people randomly assigned to one of two groups. Placebo pills to not influence people with expectations. Aspirin prevents heart attacks study: aspirin does indeed prevents h. a. "s 55% as likely.

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