This document defines and compares different statistical concepts: difference compares results between groups like height of males vs females; relationship examines how a change in one variable relates to another like height and weight; independence assesses whether two variables are unrelated such as college admission and ethnicity; goodness of fit evaluates how actual results align with a hypothetical claim or expectation. It provides examples of comparing group averages or percentages to analyze differences, relationships, and goodness of fit.

1. DIFFERENCE compare the results (height) for one group (males)
with the results of at least one other group (females).
RELATIONSHIP deals with how an increase in one
variable (height) is related to an increase or decrease in another
variable (weight).
INDEPENDENCE deals with how two variables (college admission
and ethnicity) are NOT RELATED.
GOODNESS OF FIT compare ACTUAL RESULTS with a CLAIM or a
HYPOTHETICAL expectation.
Central Tendency, Spread, or Symmetry?
Group 1
height
Group 2
height
Difference?
Individuals
height
Individuals
weight
College Admissions EthnicityNo relationship
CLAIM: 9 out of 10 dentists
recommend “X”
ACTUAL RESULTS: Only 7 out of 10
dentists actually recommended “X”
Note – generally you are comparing the average or
percentage of one group with another group or
population.