two.sample.test: Perform a two-sample hypothesis test for two independent...

In mlcollyer/chatham.bio532: Statistical analyses especially designed for BIO532, Biostatistics, at Chatham University

Description

Function performs a two-sample hypothesis test for two independent samples, based on resampling (randomization) procedure, and estimates confidence intervals. Parametric confidence intervals are also estimatd.

Usage

two.sample.test(f, data = NULL, alpha = 0.05, mu = 0, iter = 999,
  seed = NULL)

Arguments

f	A formula in the form y ~ x. The left-hand side of the formula, y, is the variable one wishes to analyze. The right-hand side, x, is a variable to describe the different samples (a factor). It is important that the formula is set up this way. Do not provide two different vectors!
data	The data frame from which the variables can be found.
alpha	The significance level for the test (accepted proability of a type I error).
mu	The hypothesized difference in population means (defaults to 0). This is the expected difference as stated in a null hypothesis.
iter	Number of resampling iterations. The oberved value counts as one iteration, so this number should be the desired number of permutations - 1. For example, if 1,000 permutations are desired, this value should be 999.
seed	If one should wish to define the random seed for the random permutations (for advanced users).

Value

The function returns a list containg means, sample sizes, variances, pooled standard error, the t-value, linear model fitted values and residuals, random mean differences, random t-values, and confidence intervals for all types of alternative hypotheses.

Author(s)

Michael Collyer

Examples

data(lowbwt)

# TST = two-sample test

TST1 <- two.sample.test(sbp ~ sex, data = lowbwt, alpha = 0.05, mu = 0, iter = 999)
summary(TST1)
plot(TST1, method = "hist", conf.int = "2T")

TST2 <- two.sample.test(sbp ~ grmhem, data = lowbwt, alpha = 0.05, mu = 0, iter = 999)
summary(TST2)
plot(TST2, method = "hist", conf.int = "2T")
plot(TST2, method = "hist", conf.int = "PT")

mlcollyer/chatham.bio532 documentation built on May 23, 2019, 2:08 a.m.