Do a t test using a statistical calculator or get a better understanding of the t test by going through this short, colorful tutorial (Under the graph, you will see a "Population 1" heading and a "Population 2" heading. We would have labeled these columns "Sample 1" and "Sample 2". Use the arrow buttons to change the mean, variance, and "population" [sample] size. If you are having trouble thinking of values, click on the tutorial's "Parameters" tab at the left of the screen. After you are done playing with values, click on the tutorial's "Simulation" tab to see if your conclusions about the impact of difference between means, variance, and sample size are correct.)
You may also want to explore the chi-square test, a statistical test that is especially useful when participants responses are type of response (e.g., helped or did not help; chose either red, green, or blue) with the following tutorials.
Tutorial 1 (more general)
Tutorial 2 (more detailed)