SAMPLE SIZE AND POWER
The question of the size of the sample, the number of observations, to be used in scientific experiments is of extreme importance. Most experiments beg the question of sample size. Particularly when time and cost are critical factors, one wishes to use the minimum sample size to achieve the experimental objectives. Even when time and cost are less crucial, the scientist wishes to have some idea of the number of observations needed to yield sufficient data to answer the objectives. An elegant experiment will make the most of the resources available, resulting in a sufficient amount of information from a minimum sample size. For simple comparative experiments, where one or two groups are involved, the calculation of sample size is relatively simple. A knowledge of the level (level of significance), level (1 power), the standard deviation, and a meaningful ‘‘practically significant’’ difference is necessary in order to calculate the sample size.