The essential difference between an experiment and an observational study is that: a. Observational studies may have confounded variables, but experiments never do.
b. In an experiment, people must give their informed consent before being allowed to participate.
c. Observational studies are always biased.
d. Observational studies cannot have response variables.
e. An experiment imposes treatments on the subjects, but an observational study does not.

e. An experiment imposes treatments on the subjects, but an observational study does not.

Step-by-step explanation:

Experiment is scientific procedure that is undertaken by an individual or a researcher in order for the person to either make a discovery, or test a hypothesis.

Observational studies are the studies whereby the researchers just observe the impact of a treatment or risk factor e.g. cohort studies. In observational study, the researchers just collect data based on what they've either heard or seen and they've no control over such variables collected whole for an experiment, treatments are applied to a group and the effects are recorded.

the number of the people going.

step-by-step explanation:

the cost to buy one movie ticket is $7. if the total cost for the movie is a function of how many people go, then the input is : the number of the people going.

it has changed from the width and the height.

step-by-step explanation: