Statistics Dictionary

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Balanced Design

In experimental design, a balanced design has an equal number of observations in all treatment groups. In contrast, an unbalanced design has an unequal number of observations in some treatment groups.

Balance is not required for analysis of variance with a single factor (i.e., one-way analysis of variance). But balance can be helpful for analysis of variance with two or more factors because:

  • Balanced designs are less vulnerable to violations of the equal variance assumption.
  • Unbalanced designs can produce correlated factors, making it hard to interpret results clearly.
See also:  Experimental Design and ANOVA