Question

1. a study reported in a popular medical journal followed 10,892 middle - aged adults over a nine - year period. at the start of the study none of the subjects had diabetes and approximately 45% of the subjects were smokers. at the end of the study, researchers found that the subjects who were smokers had a significant increased risk of diabetes. is this an observational study or an experiment? explain.
2. mcgraw hill would like to test synchronous vs asynchronous learning for a new algebra i classroom. they give a test to a group of 200 students who are brand new to the algebra i classroom. they then assign half of the students to study algebra i synchronously (with a classroom and traditional teacher) and half of the students to study algebra i asynchronously (online and at their own pace). at the end of the year, students were given the same test and the difference between the first test and the second test were compared. is this an observational study or an experiment? justify your answer.
3. a study was done to determine if eating chocolate during pregnancy has an effect on infant temperament at the age of 6 months. the study asked about 300 pregnant women to report their chocolate consumption (never/seldom, weekly, and daily). six months after they had given birth, the researchers then asked the mothers to report their child’s overall temperament (activity, smiling, fear, etc.). they determined “maternal prenatal consumption of chocolate was associated with the infant temperament in this study. mothers who reported consuming chocolate daily rated their infants at 6 months as more positively reactive and active”. is this an observational study or an experiment? explain.
4. a large study in the uk was done to determine if there was a link between cell phone usage and brain cancer. the study set out to determine if using a cell phone more, increased the likelihood of getting brain cancer. the study took about 800,000 women and asked them to report their cell phone use in 1999, in 2005, and again in 2009. in 2009, they recorded the proportion of women who had developed brain cancer. is this an observational study or an experiment? justify your answer.

Explanation:

1. The researchers only observed the subjects' smoking - status and diabetes - occurrence without manipulating any variables. So it's an observational study.
2. McGraw Hill assigned students to different learning methods (synchronous and asynchronous), which is an intervention or manipulation of the independent variable. So it's an experiment.
3. The researchers only asked pregnant women about their chocolate - consumption and later asked mothers about their infants' temperament without controlling or manipulating the chocolate - consumption. So it's an observational study.
4. The researchers only asked women to report their cell - phone use and recorded the proportion of those who developed brain cancer without manipulating cell - phone use. So it's an observational study.

Answer:

1. Observational study. Explanation: No variable was manipulated; just observed smoking and diabetes.
2. Experiment. Explanation: Assigned students to different learning methods.
3. Observational study. Explanation: No manipulation of chocolate - consumption.
4. Observational study. Explanation: No manipulation of cell - phone use.