An environmentalist measures the concentration of pollutants in a number of ponds in a region. She estimates the numbers of a
species of frog in each case, and finds a negative correlation between the pollutant concentration and the number of frogs per
unit area
Which statement BEST describes why the investigation is an observational study?
03-))
A)
There is only one independent variable in the study
B)
The researcher does not set the values of the independent variable.
It is not possible to set the concentration of pollutants in a sample of
water
D)
The researcher estimates the numbers of frogs, instead of counting them
directly
Collect Data
(MSRC Study Design And Scope