Useful Information #1
Population – entire group with some identifiable commonality(s)
Parameter – some characteristic of the population
Sample – a small group taken from the population, a subset, that is actually
studied or observed
Statistic – some characteristic of the sample, usually described as a number
Representative sample – a sample that actually
encompasses all the variability
within the population
Random sample – a sample in which every element has an equal chance
of
selection or inclusion; the intent is to gain fairness.
Stratification – technique used to manipulate a sample selection, prior to random
selection to help ensure the sample is representative
Sample size
•
Related to the possible variability within the population
•
More diverse, or variable, the larger
the sample needs to be
Observational study – merely observe and record things about the sample
Experiment – looking for a causal connection
, need to control for variability
•
Control group – constant except for the manipulated independent variable
•
Test or experimental group – manipulated
•
Placebo – used to ensure psychological unbiasness of the subject
Descriptive statistics – describes some aspect of the sample i.e. mean, standard
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 Spring '08
 SEIFRIEDTHOMASJ
 Standard Deviation, Mean

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