Description
Consider each of these study designs A and B, to answer the questions 1 – 8:
Examples were taken from Fundamentals of Statistics, by Michael Sullivan
A. Researchers Joachim Schulz and associates wanted “to investigate cancer risk among Danish cellular telephone users who were followed for up to 21 years.” To do so, they kept track of 420,095 people whose first cellular telephone prescription was between 1982 and 1995. In 2002, they recorded the number of people out of the 420,095 people who had a brain tumor and compared the rate of brain tumors in this group to the rate of brain tumors in the general population. They found no significant difference in the rate of brain tumors between the two groups. The researchers concluded “cellular telephone use was not associated with increased risk for brain tumors.”
B. Researchers Joseph L. Roti Roti and associates examined “whether chronic exposure to radio frequency (RF) radiation at two common cell phone signals…caused brain tumors in rats.” To do so, the researchers divided 480 rats into three groups. The rats in group 1 were exposed to the analogue cell phone frequency; the rats in groups 2 were exposed to the digital frequency; the rats in group 3 served as controls and received no radiation…. the rats in all three groups were treated the same except for the RF exposure. After 505 days of exposure, the researchers reported the following after analyzing the data. “We found no statistically significant increases in any tumor type, including brain, liver, lung or kidney, compared to the control group.”
Both of these studies share the same research objective of investigating an association between two variables.
1. What is the explanatory/predictor variable for each of these studies?
Rats
Danish Cell Phone Users
Tumors
Radiation from Cell Phones
2. What is the response variable for each of these studies?
Danish Cell Phone Users
Radiation from Cell Phones
Rats
Tumors
3. What is the sample for Study A?
420,095 people whose first cellular telephone prescription was between 1982 and 1995
480 rats
All cell phone users
Rats
Danish People
4. What is the sample for Study B?
All cell phone users
Danish People
420,095 people whose first cellular telephone prescription was between 1982 and 1995
480 rats
All rats
5. Even though the studies have very different samples, it is a reasonable assumption that both of these studies are trying to draw conclusions about the same population. What is the population?
480 Rats
Danish People
All rats
420,095 people whose first cellular telephone prescription was between 1982 and 1995
All cell phone users
6. Which study is done as an observational study?
Study B: Rats as Individuals
Study A: Cell Phone Users as Individuals
7. Which study is done as an experiment?
Group of answer choices
Study B: Rats as Individuals
Study A: Danish Cell Phone Users as Individuals
8. In order to conclude “causation”, that one thing caused another; you must conduct a designed experiment. Why do you think the researcher’s in study A, using Cell Phone users as individuals, chose an observational study design rather than an experiment like in study B?
Consider the following Scenario to answer questions 9 – 13.: You are commissioned by the board of directors of Paper Toys, Inc. to choose a paper for the origami frog project they will include in their Christmas catalog. The Materials Department is wondering whether they should stick with the light newspaper-like paper of their catalog to make the frog, or if they should include a heavier paper, like copy machine paper. Each type of paper will be provided in an 8 1/2” square. The folding design for the construction of the frog has already been completed and will be provided to you. It is desired that both types of paper will be tested to see which makes the better jumping frog.
9. This experiment seeks to identify the “better jumping frog”. What should be the response variable for this experiment? (Keep in mind, that if we were in person, we would be setting this up as a classroom experiment, so it must be something we could measure in a classroom. Assume that we had tape measures available.)
Distance Jumped
Type of Paper
Origami Design
10. Identify the explanatory/predictor variable.
Distance Jumped
Type of Paper
Origami Design
11. According to the wording of the question, which is your baseline or control group?
Origami Frogs made from heavier paper, like copy machine paper.
Origami Frogs made from light newspaper-like paper of their catalog.
Origami Frogs
12. Determine at least five Confounding Variables that could affect the response variable. Remember that these are variables the researcher should identify ahead of time to handle either by Direct Control or Randomization to handle their effect on the response variable.
13. After our experiment is complete and if our data and analysis indicate it an association between the type of paper used and the distance jumped, would we be able to conclude that the type of paper caused the better jumping ability of the frog? Or merely that they are associated?
Group of answer choices
No, because we don’t have all the data.
Yes, because this was an experiment.
No, because we only took a sample.
Yes, because this was an observational study.
14. Give a population and variable of interest to you.
Your variable may be part of an association, like hours of sleep related to productivity, or a stand-alone variable like the proportion of registered voters.
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