Question

ch 9* a large representative random sample of 6906 u.s. adults collected over 20 years showed that \parents reported higher levels of life satisfaction than nonparents,\ with the observed difference in life satisfaction between the two groups being statistically significant. this is an example of

a randomized comparative experiment

an observational study

a matched pairs experiment

question 17
1 pts
ch 9 in a study of human development, investigators showed two different types of movies to groups of children. crackers were available in a bowl, and the investigators compared the number of crackers eaten by children watching both movies. one movie was shown at 8 a.m. (right after the children had breakfast) and the other at 11 a.m. (right before the children had lunch). it was found that during the movie shown at 11 a.m., more crackers were eaten than during the movie shown at 8 a.m. the investigators concluded that the different types of movies had different effects on appetite. the treatment in this experiment is

the number of crackers eaten.

the time each movie was shown.

the bowls.

the different kinds of movies.

Explanation:

First Question (About the study on U.S. adults)

1. A randomized comparative experiment involves randomly assigning subjects to different treatment groups, which is not done here as the study just observes existing groups (parents vs non - parents).
2. An observational study is when we observe and measure characteristics of a population without interfering (here, we just observe the life satisfaction of parents and non - parents from a sample).
3. A matched pairs experiment involves pairing subjects and then giving different treatments, which is not the case here. So the correct answer is an observational study.

1. The number of crackers eaten is the response variable (what we measure), not the treatment.
2. The time each movie was shown is a confounding variable (it affects appetite due to meal times), not the treatment.
3. The bowls are just a container for crackers, not the treatment.
4. The treatment in an experiment is the factor that is manipulated. Here, the investigators manipulated the type of movie shown to the children, so the treatment is the different kinds of movies.

Answer:

an observational study

Question 17 (About the human development study)