Final answer:
In observational studies, researchers do not manipulate independent variables but observe the relationship between independent and dependent variables to test hypotheses.
Step-by-step explanation:
Observational studies are a research method commonly used in fields such as biology to investigate the relationship between variables without manipulation by the researcher. Among the choices provided, the true statements about observational studies are:
- (c) Observational studies have both independent and dependent variables. These are the factors being studied to see if changes in one (the independent variable) result in changes in the other (the dependent variable).
- (d) Observational studies can be used to test hypotheses. They allow researchers to gather evidence and observations to support or refute a hypothesis.
- (f) Observational studies do not involve manipulating independent variables. In these studies, the variables are observed as they naturally occur.
Options (a) and (e) are incorrect because observational studies involve independent and dependent variables, but these are not manipulated. Options (b) and (g) are also incorrect; it's a misconception that observational studies do not have controls. While they may not have experimental manipulations, they can still use control groups or techniques to account for other variables that might influence the outcome.