Chapter 1. Experimental Method Infographic Activity

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Scientific American: Psychology
Infographic Activity 1.5: The Experimental Method

The Experimental Method: Are You in Control?

The experimental method is the type of research that can tell us about cause and effects. It is different from descriptive studies in that key aspects of an experiment – participants, variables, and study implementation – are tightly controlled. An experiment typically includes at least two groups – an experimental group and a control group. This allows the researcher to isolate the effects of manipulating a single variable, called the independent variable.

When is it important to use the experimental method? Imagine you want to know if laws that ban texting while driving are worthwhile. Does texting really cause more accidents? Perhaps texting is merely correlated with higher accident rates in certain populations, such as college students, because college students are more likely to text and more likely to have accidents. In order to find out, you have to perform an experiment.

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1.1 Quiz

1. A variable that is intentionally manipulated by the researcher who is conducting an experimental study is called the ________ variable.

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2. Dr. Atelefack is conducting an experiment that examines whether increased water consumption in the hour prior to an exam has a significant impact on a participant’s exam score. She takes her participants and divides them into three groups. The first group does not drink any extra water before the exam. The second group drinks two 8-ounce cups of water in the hour before the exam. The third group drinks four 8-ounce glasses of water in the hour before the exam. After the exam is administered, she computes the average score from each of the three groups to look for significant differences. In this study, what is the dependent variable?

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3. In a “perfect” experiment, any changes in variable being measured would have been caused by changes in the variable that is manipulated by the researcher. This is almost never the case, however, as other factors called ________ variables can interfere with the outcomes.

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4. Professor Walters designs an experiment to test the effects of alcohol consumption on driving ability. He is going to have 100 participants, all of whom are over 21 years of age, divided into four groups. Each group will receive a different amount of alcohol, and then will be asked to drive a car through a closed obstacle course. The number of cones each person knocks down will be used as a measure of their driving skill. Which of the following methods would be the best way to assign each of the 100 participants to the various experimental or control groups?

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5. A subset of the population that is chosen to reflect the population of interest is called a(n):

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6. There is only one kind of research that can give us information about cause-and-effect relationships between different variables. What is it?

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7. Marvin is conducting a study to determine whether or not a new medication is effective in reducing pain associated with migraines. His study is funded by a grant from the pharmaceutical company that developed and produces the medication. Given the potential for experimenter bias in this study, what method should be employed to keep the research as objective as possible?

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8. If you were to recruit a group of participants for a study by taking every fiftieth name from your college student directory, you’d be using a ________ sample to avoid introducing bias into your study.

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