Basic Terminology

1. control group-a group used as a standard of comparison in a control experiment
2. experimental group-a group being studied to evaluate the effect of an event, substance, or technique
3. independent variable-a variable whose value determines the value of other variables; a factor that can be varied or manipulated in an experiment
4. dependent variable-the outcome variable; what you measure in the experiment and what is affected during the experiment
5. controlled variable-quantity or condition which is measured and controlled; independent variable
6. randomization-a method based on chance by which study participants are assigned to a treatment group. Randomization minimizes the differences among groups by equally distributing people with particular characteristics among all the trial arms. The researchers do not know which treatment is better. From what is known at the time, any one of the treatments chosen could be of benefit to the participant.
7. sampling error-the degree to which a sample might differ from the population
8. random error (+/-)-the irreproducibility in making replicate measurements and affects the precision of a result; the scattering of a measured value around a mean or
   average value
9. systematic error-a persistent statistical error having a nonzero mean that cannot be attributed entirely to chance but to inaccuracy inherent in the statistical system
10. experimental investigation
11. observational investigation