######################################################################################################################
# Function: TTest .
# Argument: Data set and parameter (call type).
# Description: Computes one-sided p-value based on two-sample t-test.
TTest = function(sample.list, parameter) {
# Determine the function call, either to generate the p-value or to return description
call = (parameter[[1]] == "Description")
if (call == FALSE | is.na(call)) {
# No parameters are defined
if (is.na(parameter[[2]])) {
larger = TRUE
}
else {
# Check the name of arguments
if (!all(names(parameter[[2]]) %in% c("larger"))) stop("Analysis model: Ttest test: this function accepts only one argument (larger)")
# larger argument
if (!is.logical(parameter[[2]]$larger)) stop("Analysis model: TTest test: the larger argument must be logical (TRUE or FALSE).")
larger = parameter[[2]]$larger
}
# Sample list is assumed to include two data frames that represent two analysis samples
# Outcomes in Sample 1
outcome1 = sample.list[[1]][, "outcome"]
# Remove the missing values due to dropouts/incomplete observations
outcome1.complete = outcome1[stats::complete.cases(outcome1)]
# Outcomes in Sample 2
outcome2 = sample.list[[2]][, "outcome"]
# Remove the missing values due to dropouts/incomplete observations
outcome2.complete = outcome2[stats::complete.cases(outcome2)]
# One-sided p-value (treatment effect in sample 2 is expected to be greater than in sample 1)
if (larger) result = stats::t.test(outcome2.complete, outcome1.complete, alternative = "greater")$p.value
else result = stats::t.test(outcome2.complete, outcome1.complete, alternative = "less")$p.value
}
else if (call == TRUE) {
result=list("Student's t-test")
}
return(result)
}
# End of TTest
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