Performs a one-way analysis of variance (ANOVA) to compare the means of two or more independent groups. By default, the function automatically selects between the classical Fisher ANOVA and Welch's ANOVA according to whether the group variances are judged to be homogeneous.
Usage
oneway_art(
data,
formula = NULL,
alpha = 0.05,
var_equal = NA,
rounding = 4,
verbose = TRUE
)Arguments
- data
A data frame containing the response and grouping variables.
- formula
A two-sided formula specifying the response and grouping variables.
- alpha
Numeric (default: 0.05). Significance level (range from 0 to 1).
- var_equal
A logical value passes into the
oneway_anova()to perform regular ANOVA on the ranked-response variable.- rounding
Integer (default: 4). Number of decimal places displayed in the output.
- verbose
Logical (default: TRUE). Show warnings and messages.
Value
A data frame representing the ANOVA table with the following columns:
- DF
Degrees of freedom.
- SS
Sum of squares.
- MS
Mean square.
- Fvalue
Observed F statistic.
- Fcrit
Critical F value at the specified significance level.
- Pvalue
P-value associated with the F statistic.
- signif
Significance code corresponding to the p-value.
- method
A character specifying this is an ART-ANOVA procedure.
The rows correspond to the treatment groups ("Group"), residual error ("Residuals"), and total variation ("Total").
Details
If var_equal = TRUE, Fisher's ANOVA is performed on the transformed response variable.
If var_equal = FALSE, Welch's ANOVA is performed. When var_equal = NA (the default),
homogeneity of variances is assessed using varequal::is_var_equal(), and the appropriate
test is selected automatically.
References
Wobbrock, J. O., Findlater, L., Gergle, D., & Higgins, J. J. (2011). The aligned rank transform for nonparametric factorial analyses using only ANOVA procedures. Proceedings of the SIGCHI Conference on Human Factors in Computing Systems, 2011, 143–146. https://doi.org/10.1145/1978942.1978963
Elkin, L. A., Kay, M., Higgins, J. J., & Wobbrock, J. O. (2021). An aligned rank transform procedure for multifactor contrast tests. Proceedings of the 34th Annual ACM Symposium on User Interface Software and Technology, 754–768. https://doi.org/10.1145/3472749.3474784
Examples
normality::is_normal(anorexia, weight_gain ~ therapy)
#> [1] FALSE
oneway_art(anorexia, weight_gain ~ therapy)
#> DF SS MS Fvalue Fcrit Pvalue signif p_omega2 method
#> Group 2 3996.027 1998.0135 5.087 3.1296 0.0087 ** 0.102 ART-ANOVA
#> Residuals 69 27100.973 392.7677 NA NA NA <NA> NA ART-ANOVA
#> Total 71 31097.000 NA NA NA NA <NA> NA ART-ANOVA