Lab 3 STAT 3000
Two Sample Hypothesis Testing
• Importing Data (repeat):
First download the kudzu dataset and put it in a familiar directory
(create one if you need to, or put it on the desktop).
Start R (if it's not already started) and click on the 'File' drop down
menu at the top left. Choose 'Change Directory' and then browse to
find the directory (or folder) where you stored the data file. Click on
that directory and then click 'Ok'.
Now R knows to look for the data file you will soon be referring to in
the appropriate folder.
In order to get that data into R, use the following commands:
> kudzu.df=read.csv("kudzu.csv")
> kudzu.df
Notice that the kudzu data are in two columns (with fairly long
headings) and the first column contains only 20 numbers and then a
sequence of "NA". That is because for the first sample, there are only
20 observations, whereas the second column or sample has a total of
25 observations.
To make the dataset more manageable, rename the column headings
to something shorter:
> names(kudzu.df)=c("without","with")
> kudzu.df
Notice that the names have now been changed. See page 384 of the
textbook for a description of this dataset.
• Two Sample t-Tests for Independent Samples: The built-in
function called 't.test' can also perform calculations for hypothesis
tests for the difference in population means.
