The independent t- test is a test for a difference in central location (mean) between two independent samples.
The requirements of the test are:
Data in existing Excel worksheets can be used and should be arranged in a List dataset layout or Table dataset layout. The dataset must contain a continuous scale variable and a nominal/ordinal scale variable containing two independent groups.
When entering new data we recommend using New Dataset to create a new 2 variables (1 categorical) dataset ready for data entry.
To start the test:
Excel 97, 2000, 2002 & 2003:
Select any cell in the range containing the dataset to analyse, then click Analyse on the Analyse-it toolbar, click Compare Groups then click t- test.
If the dataset is arranged using the list layout:Click Variable and select the dependent variable and click Factor and select the independent variable containing the two groups to compare.
The report shows the number of observations analysed, and, if applicable, how many missing values were excluded. Summary statistics for each sample are then shown.
The difference between the means and a confidence interval are shown to quantify the difference between the samples in terms that can be practically evaluated.
The t-statistic and hypothesis test are shown. The p-value is the probability of rejecting the null hypothesis, that the samples have the same mean, when it is in fact true. A significant p-value implies that the two samples have different means.
(click to enlarge)