PSC 041 Exam 4 Flashcards
Descriptive statistics
describing main aspects of the sample (mean, median, mode, range, STD)
Inferential statistics
draw inferences about the characteristics of a population from a sample (while controlling extent to which errors are made- do the results apply to the whole population of interest?)
Central tendency
point of value in the middle of a distribution (mean, median, mode)
Mean
average
Median
numerical middle value
Mode
most frequent response
Nominal data
measurement fits into discrete unordered categories (eye color)
Ordinal
measurement that fits into discrete categories but can be ordered/ranked along a scale (1st-8th in a race)
Interval data
measured on a scale with equal spacing between units of measurement but have no meaningful zero point (temperature)
Ratio data
measured on a scale with equal spacing but have a meaningful zero point (income $10,000)
Nominal M’s?
mode
Ordinal M’s?
mode, median
Interval M’s?
mode, median, mean
Ratio M’s?
mode, median, mean
Dispersion
extent to which scores in the distribution deviate from the mean
Standard deviation
measure of variability between scores indicating how much they differ from the mean
Z-score
standardized value to represent standard deviations from the mean
Effect size
magnitude of the difference between groups
Cohen’s d
indicates standardized difference between two means
Small effect
0.2 (58%)
Medium effect
0.5 (69%)
Large effect
0.8 (79%)
T-test
test used to compare the means of two groups of data
T-value
measure of difference between two sets expressed in units of standard error
P-value
measure of the probability of an observation lying at extreme t-values
P < 0.05
statistically significant, reject H0
P > 0.05
not statistically significant, fail to reject H0
Type I error
false positive: concluding that there is a difference when there is not
Type II error
false negative: concluding that there isn’t a difference when there really is one
