Common Errors in Statistics (and How to Avoid Them), 4th Edition

PREPARATION

The first step in data collection is to have a clear, preferably written statement of your objectives. In accordance with Chapter 1, you will have defined the population or populations from which you intend to sample and have identified the characteristics of these populations you wish to investigate.

You developed one or more well-formulated hypotheses (the topic of Chapter 2) and have some idea of the risks you will incur should your analysis of the collected data prove to be erroneous. You will need to decide what you wish to observe and measure, and how you will go about observing it. We refer here not only to the primary variables or endpoints, but to the secondary variables or cofactors that may influence the former’s values. Indeed, it is essential that you be aware of all potential sources of variation.

Good practice is to draft the analysis section of your final report based on the conclusions you would like to make. What information do you need to justify these conclusions? All such information must be collected.

The next section is devoted to the choice of response variables and measuring devices, followed by sections on determining sample size and preventive steps to ensure your samples will be analyzable by statistical methods.