An observational study can show a causal relationship. An experimental study can show a causal relationship. Circle the correct answer. A sample has large variability. The center of a sample is not close to the population center.
All samples have large variability.
The centers of all samples are on the same side of the population center. An educational researcher wants to compare the effectiveness of using different computer set-ups to help in reading comprehension. First she gives 12 students a reading comprehension test. Then she randomly assigns them to computers with different set-ups. She conducts an experiment and then retests the students and compares the increase in reading ability in each group.