EVALUATION BIASES could affect the CREDIBILITY of your results

Make sure you statistically determine the sample size required to provide reliable data, because a sample that is too small is not representative of the entire population or group. Participants will perform differently if they know they are being observed, and an observer who is not trained or given proper instruments adds to the unreliability of the data. [...]conduct your observations in the least obtrusive manner possible while still getting the information you need. To be most useful and to avoid bias, the interview design must ensure that: * the sample is representative of the population * the participants understand the questions * the participants are willing participants (their participation is not mandatory) * the interviewer is trained in interviewing techniques and knows how to record the information accurately * there is a protocol for consistency in questioning * there is a method to objectively evaluate the results of the interview.