Question

(1 point) determine whether the follow descriptions correspond to an observational study or an experiment. write \experiment\ for experiment and \observation\ for observational study. (without quotations)
(a) among a group of disabled women aged 65 and older who were tracked for several years, those who had a vitamin b12 dificiency were twice as likely to suffer severe depression than those with normal blood pressure.
answer:
(b) some people who race greyhounds give the dogs large doses of vitamin c in the belief that the dogs will run faster. investigators at the university of florida tried three different diets in random order on each of 5 racing greyhounds. they were surprised to find that when the dogs ate high amounts of vitamin c they ran more slowly.
answer:
(c) in 2002, the journal science reported that a study of women in finland indicated that having sons shortened the life spans of mothers by about 34 weeks per son, but that daughters helped to lengthen the mothers lives. the data came from church records from the period 1640 to 1870.
answer:

Explanation:

Part (a)

In this case, the group of disabled women aged 65 and older is tracked over time, and the researchers are simply observing the relationship between vitamin B12 deficiency and severe depression without intervening or manipulating any variables. So it is an observational study.

Here, investigators at the University of Florida tried three different diets (including different amounts of vitamin C) on each of 5 racing greyhounds in a random order. They are manipulating the diet (the independent variable) to see its effect on the greyhounds' running speed (the dependent variable). This is an experiment because there is active manipulation of variables.

The study uses church records from 1640 to 1870 to look at the relationship between having sons/daughters and mothers' life spans. The researchers are just observing the existing data without any intervention or manipulation of variables. So it is an observational study.

Answer:

OBSERVATION

Part (b)