There are lots of sites out there that help you to select which statistical test to use, some of which are below. You probably need to know a few basics before you start, such as what type of design you are using, what the independent and dependent variables are and the difference between types of measurement such as categorical and continuous variables. It is often worth having a look at a couple of the sites to see the different types of information you get. Clearly it makes sense to decide on what type of data you are gathering and the statistics you want to use at a very early stage of your experimental design.
Which Test is a comprehensive guide intended for clinical psychologists to help select the appropriate statistical test, based on the experimental design. Very helpful when selecting a test, but does not give details of how to analyse the data. Sponsored by the Higher Education Academy Psychology Network. Easy to use. Take the time to use the help and examples functions if you need to.
Dancey and Reidy produced an interactive Decision Chart to help you decide which test to use from Chapter on 1 way ANOVA on the companion website to Dancey and Reidy Statistics without Maths (4th Ed). This chart will ask a few questions about your design and then refer you to the relevant chapter of their textbook. Click on the Interactive Decision Chart from the left hand menu. You need to have the textbook to follow up their chapters, however you can look up the relevant chapters in a different book if you don’t have this one. For an overall view try the Wise online tutorials in statistical concepts. Useful interactive exercises on choosing the correct statistical test. Useful for basic concepts and revision for level 3 if you need it! Requires Java.
If you prefer a decision tree analysis so that you can see all the options at once, try Corston & Colman 2000 and Neill & Howell 2008. Other static guides include Intuitive Biostatistics, don’t let the title put you off…Lets you select a test based on your data and the goal of your research. Uses a grid structure to pick a test based on the type of data you are looking at such as parametric or non-parametric. Includes a useful list of points to consider, but is limited to contents of the associated text book. The American Thoracic Society has produced a good review compiling a “Best of the Web” on sites that aid in choosing the best statistical test for a given set of data, but you need a bit of time to sort through all the information.