Uses Type-2 SS by default (safe for unbalanced designs). Automatically switches to Type-3 SS when an interaction term is detected and sets the correct contrasts. Users are warned when interpreting main effects in the presence of a significant interaction.
Arguments
- formula
A formula of the form outcome ~ group1 * group2
- data
A data frame containing the variables
- type
ANOVA type: 2 or 3. Default is 2. Type 3 is automatically used when an interaction term is detected in the formula.
- conf.level
Confidence level. Default 0.95.
- context
Optional description of the study design or sampling method, echoed back in the printed report. Default NULL.
Value
An object of class statease_anova2 containing two-way
ANOVA results and interpretation. Use print() to display
the formatted report.
Examples
df <- data.frame(
score = c(23,45,12,67,34,89,56,43,78,90,11,34),
method = rep(c("Online","Traditional"), each = 6),
gender = rep(c("Male","Female"), times = 6)
)
result <- anova2_interpret(score ~ method * gender, data = df)
#> Warning: Sample size is small (n < 20). Interpret results with caution.
print(result)
#>
#> statease Two-Way ANOVA Report
#> Outcome : score
#> Factor 1 : method
#> Factor 2 : gender
#> N : 12
#> SS Type : Type-II
#>
#> Means by method:
#> Online : 45.00
#> Traditional : 52.00
#>
#> Means by gender:
#> Female : 61.33
#> Male : 35.67
#>
#> Interaction Means:
#> Female Male
#> Online 67.00 23.00
#> Traditional 55.67 48.33
#>
#> ANOVA Results:
#> method : F = 0.220 df = 1,8 not significant (p = 0.6517) eta^2 = 0.0173 (small)
#> gender : F = 2.955 df = 1,8 not significant (p = 0.1240) eta^2 = 0.2330 (large)
#> Interaction : F = 1.507 df = 1,8 not significant (p = 0.2544) eta^2 = 0.1189 (moderate)
#>
#> Assumption Checks:
#> Normality (residuals) : PASSED (Shapiro-Wilk p = 0.936)
#> Equal variances (cells) : PASSED (Bartlett's p = 0.584)
#>
#> NOTE: Assumption checks are diagnostic tools and may be
#> influenced by sample size and other characteristics of the
#> data. Passing a check does not prove that an assumption is
#> satisfied, and a warning does not automatically invalidate
#> the analysis. Interpret these results alongside your
#> knowledge of the data.
#>
#> Interpretation:
#> Main effect of method is not significant (p = 0.6517).
#> Main effect of gender is not significant (p = 0.1240).
#> Interaction (method x gender) is not significant (p = 0.2544).
#> -----------------------------------------------------------------
#>