Exam 5: Experiments and Observational Studies

Experiments use __________ to reduce the effects of confounding variables and other sources of bias that are naturally present in observational studies.

An observational study based on a sample of students in introductory psychology classes at a university in the Midwestern U.S.compared drinking behavior and hangover symptoms in men and women.To what group can the results of this study definitely be extended?

For Questions use the following narrative Narrative: Toy colors Suppose a toy company wants to know if certain colors are more appealing and attractive to toddlers than others.They decide to measure this by choosing five colors of blocks and making sets of blocks in each of the five colors.Then they found 30 toddlers to participate in the study, and they randomly assigned each toddler a block color.They observed each toddler separately at the same time of the day, and gave them no other toys to play with.They recorded the length of time each toddler played with the blocks, to see if some colors of blocks were played with longer than other colors.All toddlers in the experiment were the same age (2 years old) and an equal number of girls and boys played with each color of blocks. -{Toy colors narrative} Is this study an observational study or an experiment?

Which of the following influences on the experimental units can bias the results of an experiment?

For Questions use the following narrative Narrative: Toy colors Suppose a toy company wants to know if certain colors are more appealing and attractive to toddlers than others.They decide to measure this by choosing five colors of blocks and making sets of blocks in each of the five colors.Then they found 30 toddlers to participate in the study, and they randomly assigned each toddler a block color.They observed each toddler separately at the same time of the day, and gave them no other toys to play with.They recorded the length of time each toddler played with the blocks, to see if some colors of blocks were played with longer than other colors.All toddlers in the experiment were the same age (2 years old) and an equal number of girls and boys played with each color of blocks. -{Toy colors narrative} Name one confounding variable that was controlled for in this study.

Random assignment deals with what aspect of an experiment?

Name two ways in which an experimenter can bias the results in a poorly designed experiment.

Which of the following is a property of a confounding variable?

Random __________ is used to get a representative sample from the population of interest so the results can be extended to that population.

A group of volunteers is clearly not a random sample from the population, yet volunteers are often used in experiments.Explain why.

Name one disadvantage and one advantage of an observational study over an experiment.

An observational study that asks participants to recall their first childhood memory is a(n) __________ study.

What is one advantage of using a matched-pairs design in a randomized experiment?

Which of the following describes an experiment with little or no ecological validity?

Random sampling deals with what aspect of a study?

Which of the following is not a type of observational study?

What is the effect of recruiting volunteers to participate in a randomized experiment?

What is the main purpose of using random assignment in experiments?

What type of study often results in problems related to using the past as a source of data?

For Questions use the following narrative Narrative: BMD A recent magazine article stated that bone mineral density (BMD) may one day predict breast cancer risk in older women, according to a study in the Journal of the National Cancer Institute.Researchers followed the health of 8,905 women who were 65 or older and initially cancer free.Eventually 315 participants developed breast cancer.Women with the highest BMD were almost three times more likely to develop breast cancer, compared to the women with low BMD.(Better Homes and Gardens, October 2001, page 224.) -{BMD Narrative} Do the results of this study mean that a high bone mineral density (BMD) causes breast cancer in older women? Explain your answer.