Repeated Measures ANOVA
The Repeated Measures ANOVA is used to explore the relationship between a continuous dependent variable and one or more categorical explanatory variables, where one or more of the explanatory variables are ‘within subjects’ (where multiple measurements are from the same subject). Additionally, this analysis allows the inclusion of covariates, allowing for repeated measures ANCOVAs as well.
This analysis requires that the data be in ‘wide format’, where each row represents a subject (as opposed to long format, where each measurement of the dependent variable is represented as a row).
A non-parametric equivalent of the repeated measures ANOVA also exists; the Friedman test. However, it has the limitation of only being able to test a single factor.
Example usage
data('bugs', package = 'jmv')
anovaRM(
data = bugs,
rm = list(
list(
label = 'Frightening',
levels = c('Low', 'High'))),
rmCells = list(
list(
measure = 'LDLF',
cell = 'Low'),
list(
measure = 'LDHF',
cell = 'High')),
rmTerms = list(
'Frightening'))
#
# REPEATED MEASURES ANOVA
#
# Within Subjects Effects
# ───────────────────────────────────────────────────────────────────────
# Sum of Squares df Mean Square F p
# ───────────────────────────────────────────────────────────────────────
# Frightening 126 1 126.11 44.2 < .001
# Residual 257 90 2.85
# ───────────────────────────────────────────────────────────────────────
# Note. Type 3 Sums of Squares
#
#
#
# Between Subjects Effects
# ─────────────────────────────────────────────────────────────────
# Sum of Squares df Mean Square F p
# ─────────────────────────────────────────────────────────────────
# Residual 954 90 10.6
# ─────────────────────────────────────────────────────────────────
# Note. Type 3 Sums of Squares
#
Arguments
| data | the data as a data frame |
| rm | a list of lists, where each list describes the label (as a string) and the levels (as vector of strings) of a particular repeated measures factor |
| rmCells | a list of lists, where each list decribes a repeated measure (as a string) from data defined as measure and the particular combination of levels from rm that it belongs to (as a vector of strings) defined as cell |
| bs | a vector of strings naming the between subjects factors from data |
| cov | a vector of strings naming the covariates from data. Variables must be numeric |
| effectSize | one or more of 'eta', 'partEta', or 'omega'; use η², partial η², and ω² effect sizes, respectively |
| depLabel | a string (default: 'Dependent') describing the label used for the dependent variable throughout the analysis |
| rmTerms | a list of character vectors describing the repeated measures terms to go into the model |
| bsTerms | a list of character vectors describing the between subjects terms to go into the model |
| ss | '2' or '3' (default), the sum of squares to use |
| spherTests | TRUE or FALSE (default), perform sphericity tests |
| spherCorr | one or more of 'none' (default), 'GG', or HF; use no p-value correction, the Greenhouse-Geisser p-value correction, and the Huynh-Feldt p-value correction for shericity, respectively |
| leveneTest | TRUE or FALSE (default), test for homogeneity of variances (i.e., Levene's test) |
| TRUE or FALSE (default), provide a Q-Q plot of residuals | |
| contrasts | in development |
| postHoc | a list of character vectors describing the post-hoc tests that need to be computed |
| postHocCorr | one or more of 'none', 'tukey' (default), 'scheffe', 'bonf', or 'holm'; use no, Tukey, Scheffe, Bonferroni and Holm posthoc corrections, respectively |
| emMeans | a list of lists specifying the variables for which the estimated marginal means need to be calculate. Supports up to three variables per term. |
| emmPlots | TRUE (default) or FALSE, provide estimated marginal means plots |
| emmTables | TRUE or FALSE (default), provide estimated marginal means tables |
| emmWeights | TRUE (default) or FALSE, weigh each cell equally or weigh them according to the cell frequency |
| ciWidthEmm | a number between 50 and 99.9 (default: 95) specifying the confidence interval width for the estimated marginal means |
| emmPlotData | TRUE or FALSE (default), plot the data on top of the marginal means |
| emmPlotError | 'none', 'ci' (default), or 'se'. Use no error bars, use confidence intervals, or use standard errors on the marginal mean plots, respectively |
| groupSumm | TRUE or FALSE (default), report a summary of the different groups |
Returns
A results object containing:
| results$rmTable | a table |
| results$bsTable | a table |
| results$assump$spherTable | a table |
| results$assump$leveneTable | a table |
| results$assump$qq | |
| results$contrasts | an array of tables |
| results$postHoc | an array of tables |
| results$emm | an array of groups |
| results$groupSummary | a table |
Tables can be converted to data frames with asDF or as.data.frame(). For example:
results$rmTable$asDF
as.data.frame(results$rmTable)
Elements in arrays can be accessed with [[n]]. For example:
results$contrasts[[1]] # accesses the first element