3.1 Introduction to Data Collection Part 3

An educator wants to compare the effectiveness of computer software for teaching biology with that of a textbook presentation. She gives a biology pretest to each of a group of high school juniors, then randomly divides them into two groups. One group uses the computer, and the other studies the text. At the end of the year, she tests all the students again and compares the increase in biology test scores in the two groups. Is this an observational study or an experiment?

• Observational Study

• Experiment

A University of Helsinki (in Finland) study wanted to determine if chocolate consumption during pregnancy had an effect on infant temperament at age 6 months. Researchers began by asking 305 healthy pregnant women to report their chocolate consumption. Six months after birth, the researchers asked mothers to rate their infants' temperament, including smiling, laughter, and fear. The babies born to women who had eaten chocolate daily during pregnancy were found to be more active and "positively reactive" - a measure that the investigators said encompasses traits like smiling and laughter. Is this an observational study or an experiment?

• Observational Study

• Experiment

Researchers obtained 30 new laptops of the same brand. They chose 15 of the computers at random and adjusted their screens to the brightest setting. The other 15 laptop screens were left at the default setting - moderate brightness. Researchers then measured how long each machine's battery lasted. Is this an observational study or an experiment?

• Observational Study

• Experiment

A study of child care enrolled 1364 infants and followed them through their sixth year in school. Later, the researchers published an article in which they stated that "the more time children spent in child care from birth to age four-and-a-half, the more adults tended to rate them, both at age four-and-a-half and at kindergarten, as less likely to get along with others, as more assertive, as disobedient, and as aggressive". Is this an observational study or an experiment?

• Observational Study

• Experiment

A teacher explores this question by asking everyone in his statistics class to write down on a piece of paper the total number of hours he or she slept on each of the last three nights before taking a test. He divides the students into those who slept for an average of 8 or more hours each night and those who slept for less. Then he compares the average test scores of the two groups. Is this an observational study or an experiment?

• Observational Study

• Experiment

Aspirin prevents blood from clotting and so helps prevent strokes. The Second European Stroke Prevention Study asked if adding another anti-clotting drug named dipyridamole would help. Patients who had already had a stroke were randomly assigned to receive either aspirin only, dipyridamole only, both, or a placebo. Is this an observational study or an experiment?

• Observational Study

• Experiment