Biology 130 chapter 1

You hear a news report about a new asthma treatment. What would you want to know before you asked your doctor if this treatment was right for you?

1.Was the drug tested in a randomized clinical trial? 2. How many participants were in the trial? 3. Was there a significant difference between the effect of the new drug and the treatment used in the control group? 4. Did any of the researchers have financial ties to the manufacturer of the new asthma drug?

You carry out a clinical trial to test whether a new drug relieves the symptoms of arthritis better than a placebo. You have four groups of participants, all of whom have mildly painful arthritis (rated 6 on a scale of 1 to 10). Each group receives a daily pill as follows: group 1 (control), placebo; group 2, 15 mg; group 3, 25 mg; group 4, 50 mg. At the end of 2 weeks, participants in each group are asked to rate their pain on a scale of 1 to 10. The mean pain rating of the participants was 6.5 for the placebo, 6.0 for 15 mg of the drug, 4.5 for 25 mg of the drug, and 4.5 for 50 mg of the drug. What is your next step?

Run a statistical analysis to determine if the differences are significant.

dependent variable

The measured result of an experiment, analyzed in both the experimental and control groups

independent variable

The variable, or factor, being deliberately changed in the experimental group

You are working on an experiment to test the effect of a specific drug on reducing the risk of breast cancer in postmenopausal women. Describe your control and experimental groups with respect to age, gender, and breast cancer status.

There are many possibilities. Given the parameters, both the experimental and control groups would have to be postmenopausal females. The control group would not receive the drug; the experimental group would receive the drug (the drug is the independent variable). The main dependent variable is breast cancer.

Design a randomized clinical trial to test the effects of caffeinated coffee on brain activity. Design your study so that the results will apply to as many people in as many scenarios as possible.

There are many possibilities. The independent variable will be caffeinated coffee. The dependent variable can be any measure of brain activity (e.g., memory, alertness, problem solving). The basic design will involve two groups: caffeinated-coffee drinkers and non-caffeinated-coffee drinkers. To have the results be broadly applicable, the participants should include both sexes and a variety of ages, ethnicities, and racial groups.

What is the importance of statistical analyses?

They can be used to support or reject the hypothesis. They can be used to determine whether any observed differences between two groups are real or a result of chance.

How can two different studies investigating the same thing (e.g., the relationship, if any, between caffeinated coffee and memory) come to different conclusions?

They may have had different sample sizes. They may have used different types of participants (e.g., participants of different ages or professions). They may have used different amounts of caffeine. They may have evaluated memory differently (e.g., long-term vs. short-term memory).

The mother of a friend is a self-described "coffee addict." She recently received a diagnosis of Parkinson's disease. Does her experience negate the results of the JAMA study described in this chapter? Why or why not?

This is a case of anecdotal evidence, presenting a single person's experience in the absence of a carefully designed experiment and a large sample size. As such, this person's experience does not negate the results of the study published in JAMA.

In which of the following would you have the most confidence? A-a randomized clinical trial with 15,000 subjects B-a randomized clinical trial with 5,000 subjects C-an epidemiological study with 15,000 subjects D-an endorsement of a product by a movie star E-a report on a study presented by a news organization

a. a randomized clinicla trail with 15,000 subjects

A scientist who reads an article in a scientific or medical journal can be confident that the report has been peer reviewed a-What is a "peer-reviewed" report? Is an article in a daily newspaper a peer-reviewed article? b. What is the role of a peer reviewer of a scientific article? c. Why do scientists place so much value on the peer-review process?

a: A "peer-reviewed" scientific report is one that has been read and evaluated by other scientists. A typical newspaper has not been peer reviewed. b: A peer reviewer considers the experimental design, the data, and the analysis of the data. The reviewer's job is to ensure that the conclusions do not overreach the data and that the study is well designed and without bias. c: The peer-review process helps to ensure the integrity and quality of scientific publications, so that they can inform the scientific process moving forward.

In the studies of coffee and memory discussed in this chapter, the independent variable is _ and the dependent variable is?

caffeine; memory

Can an epidemiologist who finds a correlation between the use of tanning beds and melanoma (an aggressive form of skin cancer) in college-age women conclude that tanning beds cause skin cancer?

no; correlation is not proof of causation

You are listening to a news report that claims a new study has found convincing evidence that a particular weight-loss product is much more effective than diet and exercise. What can you infer about the "convincing evidence" in this case?

that statistical tests showed significantly more weight loss in the participants who used the weight-loss product than those who relied on diet and exercise.

In a controlled experiment, which group receives a placebo?

the control group

you carry out a clinical trial to test whether a new drug relieves the symptoms of arthritis better than a placebo. You have four groups of participants, all of whom have mildly painful arthritis (rated 6 on a scale of 1 to 10). Each group receives a daily pill as follows: group 1 (control), placebo; group 2, 15 mg; group 3, 25 mg; group 4, 50 mg. At the end of 2 weeks, participants in each group are asked to rate their pain on a scale of 1 to 10. What is the independent variable in this experiment?

the drug