Psychology: AP Psychology: Statistics and Research in Psychology
Designing studies, interpreting data, and evaluating evidence
Psychology: AP Psychology: Statistics and Research in Psychology
Designing studies, interpreting data, and evaluating evidence
Psychology - Grade 9-12
- 1
A psychologist wants to study whether sleep affects memory. She randomly assigns 80 students to either sleep 8 hours or sleep 4 hours before taking the same memory test. Identify the independent variable and the dependent variable.
The independent variable is what the researcher changes, and the dependent variable is what the researcher measures.
The independent variable is the amount of sleep, either 8 hours or 4 hours. The dependent variable is the score on the memory test because it is the outcome being measured. - 2
A survey finds that students who report higher stress levels also report lower sleep quality. The correlation between stress and sleep quality is -0.62. Explain what this correlation means and whether it proves that stress causes poor sleep.
A correlation of -0.62 means there is a moderately strong negative relationship, so higher stress tends to be associated with lower sleep quality. It does not prove that stress causes poor sleep because correlation does not establish causation. - 3
A set of reaction time scores in milliseconds is 210, 230, 230, 250, 280. Find the mean, median, and mode.
For the mean, add all values and divide by the number of values. For the median, find the middle number in order.
The mean is 240 milliseconds because the total is 1200 and 1200 divided by 5 is 240. The median is 230 milliseconds because it is the middle value. The mode is 230 milliseconds because it appears most often. - 4
A teacher tests a new study strategy in one AP Psychology class and compares the results to a different class that uses the old strategy. The students were not randomly assigned to classes. Explain one limitation of this research design.
One limitation is that preexisting differences between the classes could affect the results. Because students were not randomly assigned, differences in motivation, prior knowledge, teacher style, or class schedule could be confounding variables. - 5
A researcher wants a representative sample of all high school students in a large city. She only surveys students from one honors psychology class. Explain why this sample is biased and suggest a better sampling method.
A representative sample should reflect the larger population the researcher wants to understand.
The sample is biased because one honors psychology class may not represent all high school students in the city. A better method would be random sampling from student lists across multiple schools so that different types of students have a chance to be included. - 6
A study reports that a new anxiety treatment produced a statistically significant improvement with p < .05. Explain what p < .05 means in this context.
A p-value less than .05 means that if there were really no treatment effect, the probability of getting results this extreme by chance would be less than 5 percent. It suggests the result is unlikely to be due to random chance alone, but it does not prove the treatment works for every person. - 7
A bar graph shows the average number of words recalled by three groups: no music, classical music, and loud pop music. The loud pop music group recalled the fewest words. Write one conclusion the graph supports and one conclusion it does not support.
Graphs show patterns in data, but the research design determines whether a causal claim is justified.
The graph supports the conclusion that, in this sample, the loud pop music group recalled fewer words on average than the other groups. It does not support the conclusion that loud pop music always causes poor memory unless the study was an experiment with proper controls and random assignment. - 8
In a double-blind drug study, neither the participants nor the researchers interacting with them know who receives the real medication and who receives a placebo. Explain why this design is useful.
A double-blind design reduces bias from both participants and researchers. Participants are less likely to change behavior based on knowing their group, and researchers are less likely to unintentionally influence or interpret results differently. - 9
A memory test has a normal distribution with a mean of 100 and a standard deviation of 15. A student scores 130. Explain how far this score is from the mean in standard deviation units.
Subtract the mean from the score, then divide by the standard deviation.
A score of 130 is 30 points above the mean. Since the standard deviation is 15, the score is 2 standard deviations above the mean because 30 divided by 15 equals 2. - 10
A psychologist observes children on a playground and records how often they share toys. The psychologist does not interfere with the children. Identify the research method and explain one strength of it.
The research method is naturalistic observation. One strength is that behavior is studied in a real-world setting, so the observations may reflect how children naturally act. - 11
A study about test anxiety asks participants to sign a consent form, tells them they may quit at any time, keeps their names private, and explains the study afterward. Identify two ethical principles shown in this example.
Common ethics terms include informed consent, confidentiality, right to withdraw, protection from harm, and debriefing.
Two ethical principles shown are informed consent and confidentiality. The right to withdraw is also shown because participants are told they may quit at any time, and debriefing is shown because the study is explained afterward. - 12
A scatterplot shows a correlation of +0.10 between hours spent studying and happiness ratings. Explain what the strength and direction of this correlation suggest.
The sign shows direction, and the size of the number shows strength.
A correlation of +0.10 suggests a very weak positive relationship. As hours spent studying increase, happiness ratings may increase slightly, but the relationship is so weak that studying hours do not strongly predict happiness in this data set.