ABSTRACT
This chapter discusses the methods of deriving the important relationships are considered and methods of putting the results obtained from surveys and research to practical use for crop protection. Surveys of rodent damage in growing crops seldom directly measure actual yield losses. It is usually necessary to apply an adjustment based on either intuitive reasoning or a correction factor determined experimentally. Rice is a crop that can be subjected to rat attack at all stages of growth. Planning a crop damage sampling scheme is usually a three stage process. The first stage is to choose a suitable sampling plan. The next step is to decide how large a sample will be needed. The third step is to plan how to take the sample so that it conforms to the requirements of the sampling plan. In simple random sampling, each individual in the sample has to be drawn independently and with equal probability from the population that is under investigation.
