BIOL 373 Lecture Notes - Lecture 7: Pooled Variance, Biostatistics, Sampling Distribution
Document Summary
Compare statistics from two samples to draw conclusions about two populations. Using old concepts & adjusting them to make a new test. Examples: 1 2, does fecundity differ between short-winged and long-winged crickets. Take random samples from both populations and ask if their means differ. X 1 x 2 s x 1 x2. We are interested in the difference between 1 & 2. Take repeated samples from the two populations and calculate the difference between the sample means each time. Gives a sampling distribution of the difference between 1 & 2: mean of this distribution: ( x 1 x 2)= 1 2 x1 x 2 o. : standard error of the difference between sample means. We must therefore estimate a common variance: pooled variance, sp. Estimated standard error of the sampling distribution of differences between the means: Corrects for sample size to get the standard error of difference between sample.
