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Stats 13 vocab
States vocabulary
| Question | Answer |
|---|---|
| Observational study | a study based on data with no manipulation used |
| retrospective study | subjects are selected and than their previous conditions or behaviors are determined. Not based on random sampling Focus on estimating differences between groups or associations between variables |
| prospective study | subjects are followed to observe future outcomes. No treatment are applied. Not an experiment. Focus on estimating differences among groups during the study |
| experiment | manipulates factor levels to create treatments, randomly assigns subjects to these treatments levels. Compares the responses of subject groups across treatments levels. |
| random assignment | an experiment must assign experimental units to treatment groups at random. |
| factor | a variable whose levels are controlled by the experimenter. |
| response | a variable whose values are compared across different treatments. |
| experimental units | individuals on whom an experiment is performed. Can be called subjects or participants |
| level | the specific values that the experimenter chooses for a factor |
| treatment | the process, intervention, or other controlled circumstance applied to randomly assigned experimental units. the Explanatory variable |
| Principles of experimental design | Control, Randomize, Replicate, Block |
| Control | make conditions as similar as possible for all treatment groups. |
| Randomize | equalize the effects of unkown or uncontrollable source of variation |
| Replicate | over as many subjects as possible. Results from a single subject are just anecdotes. |
| Block | the only difference in the control group and the experimental group is the 1 thing we are testing. |
| statistically significant | when an observed difference is too lrge for us to believe that it is likely to have occured naturally. |
| control group | the experimental units assigned to a baseline treatment level. |
| Blinding | don't let the patient know if they are in the control group or the experimental group. |
| single-blind, double blind | these are two main classes of individuals who can affect the outcome of an experiment: those who could influence the results (subjects, technicians). Those who evaluate the results (juges, physicians) |
| placebo effect | people think they feel differently just because they know they are being tested |
| 2 ways to replicate | use several subjects, or replicate the entire experiment on another group |
| extraneous factors | factors that are not being experimented with but may be influencing the outcome. Eliminate this by blocking. |
| confounded variables | factors that can't be distinguished between which one is affecting the outcome. |
| placebo | a treatment known to have no effect. |
| match | reduces unwanted variation |
| 2 types of designs | completely randomized design, and randomized block design |
| completely randomized design | all experimental units have an equal chance of receiving any treatment |
| randomized block design | the randomization occurs only within blocks |
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