Module 6 REVIEW

• 6-1 What does it mean when we say two things are correlated, and what are positive and negative correlations?

• Correlation is the degree to which two variables are related, and how well one predicts the other.
• In a positive correlation, two factors increase or decrease together. In a negative correlation, one variable increases as the other decreases.
• A correlation coefficient describes the strength and direction of a relationship between two variables, from +1.00 (a perfect positive correlation) through zero (no correlation at all) to −1.00 (a perfect negative correlation).
• The relationship may be displayed in a scatterplot, in which each dot represents a value for the two variables.

• 6-2 Why do correlations enable prediction, but not cause-effect explanation?

• Correlations enable prediction because they show how two factors are related—either positively or negatively. A correlation can indicate the possibility of a cause-effect relationship, but it does not prove the direction of the influence, or whether an underlying third factor may explain the correlation.

• 6-3 What are illusory correlations, and what is regression toward the mean?

• Illusory correlations are random events that we notice and falsely assume are related.
• Regression toward the mean is the tendency for extreme or unusual scores to fall back toward their average.

• 6-4 What are the characteristics of experimentation that make it possible to isolate cause and effect?

• To discover cause-effect relationships, psychologists conduct experiments, manipulating one or more variables of interest and controlling other variables.
• Using random assignment, they can minimize confounding variables, such as preexisting differences between the experimental group (exposed to the treatment) and the control group (given a placebo or different version of the treatment).
• The independent variable is the factor the experimenter manipulates to study its effect; the dependent variable is the factor the experimenter measures to discover any changes occurring in response to the manipulation of the independent variable.
• Studies may use a double-blind procedure to avoid the placebo effect and researcher’s bias.
• An experiment has validity if it tests what it is supposed to test.

Multiple-Choice Questions

1. Which of the following is an example of negative correlation?
   1. People who spend more time exercising tend to weigh less.
   2. Teenage females tend to have fewer speeding tickets than teenage males.
   3. Students with lower IQ scores tend to have lower grades.
   4. As hours studying for a test decrease, so do grades on that test.
   5. Students’ shoe sizes are not related to their grades.
2. In an experiment to test the effects of room temperature on test performance the independent variable is
   1. the scores on the test before the experiment begins.
   2. the scores on the test at the end of the experiment.
   3. whether the teacher was male or female.
   4. the temperature of the room.
   5. the style of test (multiple choice versus essay).
3. Researchers have discovered that individuals with lower income levels report having fewer hours of total sleep. Therefore,
   1. income and sleep levels are positively correlated.
   2. income and sleep levels are negatively correlated.
   3. income and sleep levels are inversely correlated.
   4. income and sleep levels are not correlated.
   5. lower income levels cause individuals to have fewer hours of sleep.
4. Which of the following correlation coefficients represents the strongest relationship between two variables?
   1. +0.30
   2. +0.75
   3. +1.3
   4. –0.85
   5. –0.05
5. The purpose of random assignment is to
   1. allow participants in both the experimental and control groups to be exposed to the independent variable.
   2. ensure that every member of the population has an equal chance of being selected to participate in the research.
   3. eliminate the placebo effect.
   4. reduce potential confounding variables.
   5. generate operational definitions for the independent and dependent variables.
6. In a drug study, neither the participants nor the person distributing the pills knows who is receiving the new drug and who is receiving the placebo. This type of research design is said to be a(n) _____ study.
   1. correlational
   2. confounding
   3. double-blind
   4. single-blind
   5. illusory

Practice FRQs

1. Researchers surveyed 800 high school students enrolled in AP^® Psychology to determine whether students with higher scores on anxiety scales had lower scores on standardized tests. Students with higher scores on anxiety scales were indeed found to have lower scores on standardized tests. Explain how each of the following terms or phrases applies to the situation described above:
   • Random sampling
   • Generalization
   • Correlation does not mean causation

Answer

1 point: The researchers could use random sampling to choose the 800 students for their survey. The names could, for example, be chosen in such a way (say, every fiftieth name of those taking the course) to ensure that every test taker has the same chance of being selected. Page 47

1 point: If the random sample is used, it will be representative of the wider population from which it was drawn. Thus, the researchers will be able to generalize the results from their sample to the wider population of AP^® Psychology students. The results of the survey would only apply to AP^® Psychology students, not high school students in general. Pages 70–71

1 point: Even if anxiety and test scores correlate positively, the researchers would not be able to say that anxiety caused the lower standardized test scores. Page 53

2. Ms. Ledbetter wants to determine if the new review activity she developed will improve student performance on unit exams. She randomly separates 160 students into two groups. Group A reviews for the unit exam in the traditional manner they have always used. Group B participates in the new review activity. After reviewing, both groups are given the same unit exam and their scores are compared. Explain how the following terms relate to this study:
   • Independent variable
   • Dependent variable
   • Control group

(3 points)