Decision Trees for Fundamental Statistics
To Select a Parametric Statistic
to Evaluate Group Differences
Frequency
Distribution Table
Present entire
distribution
Table or graph?
z-score Test
Is σ known?
Bar Graph
Scale of
measurement?
Single-Sample t-Test
Histogram
or Polygon
Skewed, open-ended,
or undetermined
scores?
Scale of
measurement?
Central tendency
Ordinal
How many scores for each
subject?
Two
Related-Samples t-Test
Mean
Median
Repeated-Measures
ANOVA
Mode
Related-Samples t-Test
Summarize entire
distribution
Standard
How many separate
samples?
Two
Matched or independent
samples?
Deviation
What measure of
central tendency?
Variability
Median
Independent-Measures tTest
Semi-interquartile
Range or SemiInterquartile
range or Range
Range
Repeated-Measures
ANOVA
Nominal scale?
None
Matched or independent
samples?
z-Score
Single-Factor ANOVA
How many independent
variables?
Describe individual
score
Two-Factor ANOVA
Percentile Ranks
Chi-Square
Goodness of Fit
How many categories of
measurement?
Pearson Correlation
Measure linear or
monotonic
relationship?
Both variables
measured on interval
or ratio scale?
How many
dichotomous
variables?
How many scores for
each subject?
Spearman Correlation
Sign Test
Both variables
measured on ordinal
scales?
Data consist of 2
scores for each
individual
Binomial Test
If possible, rank order
both variables and
use Spearman.
Otherwise, convert to
frequency data and
use chi-square test for
independence.
Can difference scores be
ranked?
How many separate
samples?
Two
Yes
Matched or independent
samples?
Point-Biserial
Correlation
Wilcoxon Test
Mann-Whitney
Can scores be ranked
with few tied values?
No
Chi-Square Test for
Independence
Median Test
Phi-Coefficient
Chi-Square Test for
Independence
Data consist of
frequency values for
each category
Chi-Square Test for
Independence
Independent samples
only
Are scores discrete or
continuous?
Median Test
To Select a Statistic to Measure the
Relationship Between Two Variables
Download a copy of this poster at the department website:
http://uca.edu/psychology/concept-maps/
To Select a Nonparametric Statistic
to Evaluate Group Differences