At the beginning of any study, these questions usually come to the researcher's mind; How many samples should be taken to conduct this study? How are these samples selected from the target population? How I can collect the required data? In this article, we are going to
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At the beginning of any study, these questions usually come to the researcher's mind; How many samples should be taken to conduct this study? How are these samples selected from the target population? How I can collect the required data? In this article, we are going to answer these questions.
In order to choose the appropriate sample size, attention should be paid to the statistical method with which the data is to be analyzed. In the surveys, the researcher intends to estimate the desired average or prevalence in the population with 95% confidence interval. There are two formulas for determining the sample size in surveys that are referred to. In studies, the aim is to compare the average or prevalence between different groups. In each study, according to which statistical test to use for data analysis, there is a specific formula for determining the sample size, some of which are mentioned in this article.
In order to choose the sampling method from a statistical point of view, attention should be paid to the type of research, in surveys and cross-sectional observational studies, the samples should be randomly selected from among the members of the population. Otherwise, these samples will not be representative of the target population. But in interventional studies, random sampling method is not considered. Rather, there are inclusion criteria, and any person or animal (in veterinary studies) who meets these criteria can enter the study. After the members enter the intervention study, these members should be randomly assigned to different treatments.
The required data to conduct research can be collected through examination, observation, experiments or interviews. A questionnaire must be designed for the interview. In designing the questionnaire, attention should be paid to the validity and reliability of the questions.
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