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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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