Source: Statistics at Square One (BMJ online)
How to access: This is free to access from the above link.
Contents: This is one chapter in Statistics at Square One (online). This section discusses two-sample t-test, Welch's test (i.e. unequal variance between groups) and one-sample t-test (paired data).
Example(s) used in this: Transit time food through the gut
Prior math/stat knowledge to fully understand matrials: t-distribution, hypothesis testing. Those are also covered in this online book. Thus, no prior statistical or mathematical knowledge would be required, if the previous sections of this online book are referred.