Read pages 266 and 267 below then discuss the table on page 267. Page 1 of 10
1. Many students insist that they study better when listening to music. Mr. Bowman doubts this claim and suspects that listening to music actually hurts academic performance. Presented below are four possible studies that Mr. Bowman is going to use to address this question at Hinsdale Central. In each case, the response variable will be the student s GPA at the end of the semester. Suppose that for each design that the mean GPA for those who listened to music while studying was significantly lower than the mean GPA for those students who didn t listen to music while studying. Comment on what we can conclude from each design. Design 1: Get all the students in AP calculus and AP Statistics classes to participate in a study. Ask them whether or not they study with music on and then divide them into two groups based on their answers to this question. Design 2: Select a random sample of students from Central to participate in a study. Then ask them whether or not they study with music on and then divide them into two groups based on their answers to this question. Design 3: Get all the students in AP calculus and AP Statistics classes to participate in a study. Randomly assign half the students to listen to music while studying for the entire semester and have the remaining half abstain from listening to music while studying. Page 2 of 10
Design 4: Select a random sample of students from Central to participate in the study. Randomly assign half the students to listen to music while studying for the entire semester and have the remaining half abstain from listening to music while studying. A well designed experiment tells us that changes in the explanatory variable cause changes in the response variable. However, sometimes the specifics of the experiment are not realistic and only apply to the results of the experiment and thus limit our ability to apply conclusions from the experiment to a larger population. This is seen in the next example. 2. When new products are being developed for use by humans, the products are often tested on animals first. Suppose an experiment on mice determines that aspirin reduces the risk of cancer. Comment on drawing conclusions with aspirin reducing the risk of cancer in humans. Consider the following example. 3. Doctors have noticed that people who frequently visit tanning salons are at a much greater risk for skin cancer. But are the tanning beds really the cause? a. Identify any potential confounding variables in this situation. b. Discuss how you could conduct an experiment to help determine if exposure in tanning salons increases the risks for skin cancer. Comment on an issues you see with such an experiment. Page 3 of 10
Sometimes it is unethical or morally wrong to conduct an experiment to establish causation such as the previous example. So how then can we establish causation when it is unethical to conduct an experiment on humans? Determining if smoking causes lung cancer was such a situation. Here is what researchers have observed: The association is strong. The association between smoking and lung cancer is very strong. The association is consistent. Many studies of different kinds of people in many countries link smoking to lung cancer. That reduces the chance that some other variable specific to one group or one study explains the association. Larger values of the explanatory variable are associated with stronger responses. People who smoke more cigarettes per day or who smoke over a longer period get lung cancer more often. People who stop smoking reduce their risk. The alleged cause precedes the effect in time. Lung cancer develops after years of smoking. The number of men dying of lung cancer rose as smoking became more common, with a lag of about 30 years. Lung cancer kills more men than any other form of cancer. Lung cancer was rare among women until women began to smoke. Lung cancer in women rose along with smoking, again with a lag of about 30 years, and has now passed breast cancer as the leading cause of cancer death among women. The alleged cause is plausible. Experiments with animals show that tars from cigarette smoke do cause cancer. Medical authorities do not hesitate to say that smoking causes lung cancer. The U.S. Surgeon General states that cigarette smoking is the largest avoidable cause of death and disability in the United States. The evidence for causation is overwhelming but it is not as strong as the evidence provided by well-designed experiments. Conducting an experiment in which some subjects were forced to smoke and others were not allowed to would be unethical. In cases like this, observational studies are our best source of reliable information. There are other Data Ethics examples given in your text on page 270. Be sure to read them. Case Study Early research showed that magnetic fields affected living tissue in humans. Some doctors have begun to use magnets to treat patients with chronic pain. Scientists wondered whether this type of therapy really worked. They designed a study to find out. Fifty patients with chronic pain were recruited for the study. A doctor identified a painful area on each patient and asked him or her to rate the pain on a scale from 0 (mild pain) to 10 (severe pain). Then, the doctor selected a sealed envelope containing a magnet from a box that contained both active and inactive magnets. That way, neither the doctor nor the patient knew which type of magnet was being used. The chosen magnet was applied to the site of the pain for 45 minutes. After treatment, each patient was again asked to rate the level of pain from 0 to 10. 29 patients were given active magnets and 21 patients received inactive magnets. All but one of the patients rated their initial pain as an 8, 9, or 10. Because their initial pain ratings were so similar, scientists decided to focus on patients final pain ratings. Here they are, grouped by the type of magnet used. Page 4 of 10
Discuss the design of this experiment and comment on the conclusions you might draw from the data. Page 5 of 10
Read pages 266 and 267 below then discuss the table on page 267. Page 6 of 10
1. Many students insist that they study better when listening to music. Mr. Bowman doubts this claim and suspects that listening to music actually hurts academic performance. Presented below are four possible studies that Mr. Bowman is going to use to address this question at Hinsdale Central. In each case, the response variable will be the student s GPA at the end of the semester. Suppose that for each design that the mean GPA for those who listened to music while studying was significantly lower than the mean GPA for those students who didn t listen to music while studying. Comment on what we can conclude from each design. Design 1: Get all the students in AP calculus and AP Statistics classes to participate in a study. Ask them whether or not they study with music on and then divide them into two groups based on their answers to this question. Design 2: Select a random sample of students from Central to participate in a study. Then ask them whether or not they study with music on and then divide them into two groups based on their answers to this question. Design 3: Get all the students in AP calculus and AP Statistics classes to participate in a study. Randomly assign half the students to listen to music while studying for the entire semester and have the remaining half abstain from listening to music while studying. Page 7 of 10
Design 4: Select a random sample of students from Central to participate in the study. Randomly assign half the students to listen to music while studying for the entire semester and have the remaining half abstain from listening to music while studying. A well designed experiment tells us that changes in the explanatory variable cause changes in the response variable. However, sometimes the specifics of the experiment are not realistic and only apply to the results of the experiment and thus limit our ability to apply conclusions from the experiment to a larger population. This is seen in the next example. 2. When new products are being developed for use by humans, the products are often tested on animals first. Suppose an experiment on mice determines that aspirin reduces the risk of cancer. Comment on drawing conclusions with aspirin reducing the risk of cancer in humans. Consider the following example. 3. Doctors have noticed that people who frequently visit tanning salons are at a much greater risk for skin cancer. But are the tanning beds really the cause? a. Identify any potential confounding variables in this situation. b. Discuss how you could conduct an experiment to help determine if exposure in tanning salons increases the risks for skin cancer. Comment on an issues you see with such an experiment. Page 8 of 10
Sometimes it is unethical or morally wrong to conduct an experiment to establish causation such as the previous example. So how then can we establish causation when it is unethical to conduct an experiment on humans? Determining if smoking causes lung cancer was such a situation. Here is what researchers have observed: The association is strong. The association between smoking and lung cancer is very strong. The association is consistent. Many studies of different kinds of people in many countries link smoking to lung cancer. That reduces the chance that some other variable specific to one group or one study explains the association. Larger values of the explanatory variable are associated with stronger responses. People who smoke more cigarettes per day or who smoke over a longer period get lung cancer more often. People who stop smoking reduce their risk. The alleged cause precedes the effect in time. Lung cancer develops after years of smoking. The number of men dying of lung cancer rose as smoking became more common, with a lag of about 30 years. Lung cancer kills more men than any other form of cancer. Lung cancer was rare among women until women began to smoke. Lung cancer in women rose along with smoking, again with a lag of about 30 years, and has now passed breast cancer as the leading cause of cancer death among women. The alleged cause is plausible. Experiments with animals show that tars from cigarette smoke do cause cancer. Medical authorities do not hesitate to say that smoking causes lung cancer. The U.S. Surgeon General states that cigarette smoking is the largest avoidable cause of death and disability in the United States. The evidence for causation is overwhelming but it is not as strong as the evidence provided by well-designed experiments. Conducting an experiment in which some subjects were forced to smoke and others were not allowed to would be unethical. In cases like this, observational studies are our best source of reliable information. There are other Data Ethics examples given in your text on page 270. Be sure to read them. Case Study Early research showed that magnetic fields affected living tissue in humans. Some doctors have begun to use magnets to treat patients with chronic pain. Scientists wondered whether this type of therapy really worked. They designed a study to find out. Fifty patients with chronic pain were recruited for the study. A doctor identified a painful area on each patient and asked him or her to rate the pain on a scale from 0 (mild pain) to 10 (severe pain). Then, the doctor selected a sealed envelope containing a magnet from a box that contained both active and inactive magnets. That way, neither the doctor nor the patient knew which type of magnet was being used. The chosen magnet was applied to the site of the pain for 45 minutes. After treatment, each patient was again asked to rate the level of pain from 0 to 10. 29 patients were given active magnets and 21 patients received inactive magnets. All but one of the patients rated their initial pain as an 8, 9, or 10. Because their initial pain ratings were so similar, scientists decided to focus on patients final pain ratings. Here they are, grouped by the type of magnet used. Page 9 of 10
Section 4.3 Using Studies Wisely Discuss the design of this experiment and comment on the conclusions you might draw from the data. Page 10 of 10