R/t_ci.R

In jmiahjones/lunch.time: Analyze Survey Data related to Eating Trends

#' Create Confidence Interval using t Distribution
#'
#' @param data One column of data to create a confidence interval of the mean for.
#' @param alpha Alpha level of the confidence interval.
#' @param rounding_places How many places to round each side of the confidence interval to.
#'
#' @return A confidence interval for the mean based on the t-distribution.
#' @export
#' @importFrom stats qt sd
t_ci <- function(data, alpha, rounding_places) {
  n <- length(data)
  moe <- stats::qt(1-(alpha/2), df=n-1) * stats::sd(data) / sqrt(n)
  lower <- mean(data) - moe
  upper <- mean(data) + moe

  return(
    paste(
      "(", round(lower, rounding_places), ", ",
      round(upper, rounding_places), ")",
      sep=""
    )
  )
}