1. Which of the following is the independent variable in the study?
A. Time of exam administration
B. Noise level Correct
C. Exam score
D. Exam difficulty
Explanation
In experimental research, the independent variable is the factor that the researcher manipulates to observe its effect on the dependent variable, which is the outcome measured. In this study, the professor deliberately varied the noise level outside the classroom (absolute silence, low-level noise, and moderate noise) to determine its impact on exam scores. Therefore, the noise level is the independent variable, as it is the condition being controlled and tested. The other options, such as time of exam administration, exam score, and exam difficulty, are not manipulated in the study design, with exam score being the dependent variable and the others potential confounds or constants.
2. A professor designed a study to determine whether noise level outside the classroom affects exam scores. Three 80-question exams were administered at various points in the course, in the room in which the course was taught, during regular class time. The professor arranged for absolute silence outside the classroom during the first exam, low-level noise during the second, and moderate noise during the third. The professor then compared exam scores across the three exams. Which of the following is a potential confound in the study?
A. Absolute silence outside the classroom
B. Course difficulty
C. Room in which the exam was given
D. Time in the semester that the exam was given Correct
Explanation
A confound is an extraneous variable that varies systematically with the independent variable and could influence the dependent variable, potentially skewing the results. In this study, the time in the semester when each exam was administered could act as a confound because students' knowledge, preparation, or fatigue levels may change over the course of the semester. For example, students might perform better on later exams due to increased familiarity with the material or worse due to cumulative stress, independent of the noise level. Absolute silence is part of the independent variable, course difficulty is not mentioned as varying, and the room was consistent, making time in the semester the most likely confound.
3. If the results of a study are statistically significant, they
A. most likely cannot be replicated
B. have practical significance
C. are the opposite of what was predicted
D. are most likely not due to chance Correct
Explanation
Statistical significance in a study indicates that the observed results are unlikely to have occurred by random chance, typically determined by a p-value below a threshold (e.g., 0.05). This suggests that the findings reflect a real effect of the independent variable on the dependent variable. However, statistical significance does not guarantee practical significance (real-world importance), replication, or contradiction of predictions. It simply means the results are reliable enough to reject the null hypothesis, making 'most likely not due to chance' the correct choice.
4. Dr. Gregory is utilizing a procedure that identifies groups or clusters of abilities in her intelligence research. Which of the following techniques is Dr. Gregory most likely using?
A. Factor analysis Correct
B. Standardization
C. Chi-squared test of independence
D. Criterion testing
Explanation
Factor analysis is a statistical technique used to identify underlying relationships or clusters of variables, such as grouping related abilities in intelligence research. Dr. Gregory is likely using this method to uncover patterns, such as verbal or spatial intelligence factors, within a set of test scores. Standardization involves setting norms for a test, the chi-squared test assesses relationships between categorical variables, and criterion testing evaluates test validity against an external standard, none of which focus on clustering abilities like factor analysis does.
5. A class of ten students takes an exam on which nine of the students earn scores in the range of 70-80. One student earns a perfect score of 100. In examining the test scores, the professor notices that the perfect score has the largest effect on which of the following measures?
A. Mean Correct
B. Median
C. Mode
D. Percentile rank
Explanation
The mean is the average of all scores and is sensitive to extreme values, such as the perfect score of 100, which will significantly increase the mean compared to the tightly clustered scores between 70 and 80. The median, representing the middle score, is less affected by outliers and would likely remain in the 70-80 range. The mode, the most frequent score, and percentile rank, which indicates relative position, are also minimally impacted by a single extreme score. Thus, the mean is most affected by the outlier.