For each study description below, identify the population and the sample. a. A researcher recruits students from a fifth-grade class at an elementary school to examine math abilities on a standardized...

For each study description below, identify the population and the sample.

a. A researcher recruits students from a fifth-grade class at an elementary school to examine math abilities on a standardized test in children who are 9–10 years old.

b. A researcher recruits college students from the university subject pool to test the effect of time pressure on accuracy in completing a task.

c. Older adults are recruited from a retirement center to examine sources of anxiety in retirees. Anxiety is measured using survey items in which the participants rate their level of anxiety on a 1 to 7 scale for different issues that might be anxiety inducing (e.g., financial security, failing health, etc.).

d. Patients who have suffered a traumatic brain injury (TBI) are included (with their consent) in a study of how one’s diet after the injury affects recovery time (measured in number of days they stay in the hospital after their injury) from a local hospital.