Chapter 1: Stats and Research Methods Review Flashcards
Variable
anything that can take on different values
types of variables (levels of measurement)
categorical (binary, nominal, ordinal)
continuous (interval, ratio)
interval: equal intervals, no true 0 (F)
ratio: equal intervals, true 0
measurement error
difference between observed and true value
reliability & validity
Reliability refers to the consistency of a measure (whether the results can be reproduced under the same conditions). Validity refers to the accuracy of a measure (whether the results really do represent what they are supposed to measure)
experimental vs correlational design
experimental: manipulate the IV to see affect on DV, can infer causation
- true experiment: random assignment
- quasi-experiment: no randomization, used in applied settings
correlational: no manipulation, used in applied settings. measures variable of interest to see if pattern of covariation is consisten with hypothesis/explanation. cannot infer causation
methods of data collection
between-subjects: between groups, independent design, none of the same people in each group
within-subjects: within group, repeated measures design, same people in each group measured at different times, they are their own control
types of variation
systematic variation: variation that can be explained by the model
unsystematic variation: variation not explained by the model
randomization
random assignment: makes groups equal on extraneous variables, greatly improves causal inference
counterbalancing: eliminate order effects (practice, boredom), improves causal inference, determines which goes to 1st and 2nd condition first
frequency distributions
normal, bimodal, rectangular, positively skewed (tail at high end), negatively skewed (tail at low end)
4 qualities of a distribution
- central tendency (representative values): mean, median, mode
- dispersion (spread): range, variance, SD
- skewness: positive, negative
- kurtosis: more or fewer extreme scores relative to a distribution
- platykurtic: low degree of peakedness (kurtosis<0)
- mesokurtic: normal distribution (kurtosis = 0)
- leptokurtic: high degree of peakedness (kurtosis >0)
measures of central tendency
describe typical, average, representative scores
convey info about the center of a distribution
mean, median, mode
Mode
score that occurs most frequently
useful descriptive statistic w/ nominal (categorical) variables
major/minor mode sometimes used
median
score at the 50th percentile of a distribution
- for odd sets, its the middle number
- for even sets, its the average of the two middle numbers
mean
average
measures of dispersion
describes the spread of scores
are scores clumped together around the mean or are they dispersed?
range, variance, SD
