does some one mind checking my work? it's real simple Stats vocab. thank you!

Question

Determine whether the given description corresponds to an observational study or an experiment:

(just as a refresher, observational means passive and experiment means active)

1.)much contoversy arose over a study of patients with syphilis who were not given a treatment that could have cured them. their health was followed for years after they were found to have syphilis
my answer: Observational
My reason: The scientists who studied the patients did not try to alter the outcome, there for they were passive.

2.) The Bureau of Weights and Measures randomly selects gas stations and obtains 1 gallon of gas from each pump. The amount pumped is measured for accuracy.
My answer: Observational
My reason: The BWM did not effect the outcome or change the variables in any way, there for they were passive

3.) Cruise ship passengers are given magnetic bracelets, which they agree to wear in an attempt to eliminate or diminish the effects of motion sickness.
My answer: Experiment
My reason: The variable (whether or not they have braclets) is changed, there fore being active.

Thats all for now. Thank you for your time!

Answer 1

I agree with 1 and 2.

3. Since it has an independent variable (wearing bracelets) and a dependent variable (motion sickness), it could be considered an experiment, but a poorly constructed one without a control group.

An independent variable is the potential stimulus or cause, usually directly manipulated by the experimenter, so it could also be called a manipulative variable.

A dependent variable is the response or measure of results.

Extraneous variables — other than the independent variable — potentially can affect the dependent variable, so they must be controlled. If possible, you try to keep them constant between the experimental and control group.

The experimental group receives the independent variable.

The control group is similar to experimental, except it does not receive the independent variable. Extraneous variables are balanced between experimental and control groups.