Statistics

Statistics

descriptive statistics: ways to describe larger amounts of data (graphs, tables)
inferential statistics: generalizing beyond experimental measures
population: all individuals of interest to a study
sample: a representative set of individuals from pop.
random sampling + random assignment
observational studies
- compare 2 variables to determine if a relationship exists
- does not prove causation
- not manipulated by experimenter
confounding variables
experimental studies
- independent variable: experimenter changes
- dependent variable: experimenter measures
histograms
- positive skew (to the left)
- negative skew (to the right)
- normal
central tendencies: central point of distribution
- mean
- use median if distribution is skewed / has outliers
- use mode when describing shape of distribution
variability: how scattered the scores are around the central point
- range
- interquartile range
- standard deviation
- mean, find distance from mean, square it
- multiplying by a constant will multiple sd by that constant
- variance: sd^2
SS: sum of squared deviations
degrees of freedom: number of scores free to vary
- sample variance: ss / n-1
- population variance: ss / n