Wednesday

April 23, 2014

April 23, 2014

Posted by **Gavin** on Monday, January 21, 2013 at 8:54pm.

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!

- Statistics -
**PsyDAG**, Tuesday, January 22, 2013 at 5:37pmI 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.

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