1. Question: Grades of two courses for the same 500 students are listed in file "3w_exercise2.xls". Perform a t-test, and plot the means and standard errors in a bar graph.
2. Download the data file (in excel format, file name: 3w_exercise2.xls) for this exercise
3. Tips for this exercise
1. This exercise asks you to compare the means of two samples of data.
2. To perform a t-test, from the pull-down menu, choose Tools - Data Analysis... - T-test: paired two sample for means. This t-test is sometime also called within subject t-test.
3. To plot mean and standard error (SE), you have to calculate standard error (t-test only gives you mean values for each of the two groups). From the pull-down menu, choose Tools - Data Analysis... - Descriptive Statistics to perform this test on both samples of data.
4. To create a bar chart for mean and SE, you might want to create a new table to include data for means and SEs for both groups.
you create the bar chart for mean, double click on the bar (both bars should be
“selected”) to open a dialogue box which includes the function for Y error
bars. From "Y error bars" menu, choose "custom" to input
the data address range
for SE (highlight the TWO SEs, which should be located adjacent to each other). Do the same thing for both + and – part.