Advanced Statistics - Biology 6030

Bowling Green State University, Fall 2017

t-test

Uses

Parametric methods for the comparison of sample means

How this is done

Consider the situation where you wish to compare 2 samples, each containing n values. You are hoping to statistically evaluate whether these samples could have been derived from the same underlying distribution or whether this scenario is unlikely. You specifically test the Ho: µ1 = µ2. To test the null hypothesis that the two sample means are derived from the same population, we will place the difference between the two means within the context of the population's standard deviation. Depending on the samples N these means should be found within a certain confidence interval.

Step-by-step: Note that when you collect small data sets from the same underlying, normal distribution, the means of these samples will all vary slightly due to chance differences in the actual values sampled. Also variances from different samples will differ from each other due to chance alone. As data points are normally distributed around their sample means with a given variance s2=S(Yi-)/n-1, so the sample means will be normally distributed around a mean of means with a given standard error SE = s/

Assumptions

Parametric Technique: homoscedasticity, normality or large N Worksheet: t-Test

last modified: 2/10/14
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