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

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