 For calculating sample size, if study variable is a proportion and if we are doing it for a single group, then this is the formula. The example is prevalence of anemia. Here in this formula, z to alpha is standard normal DV8, which is given by the value 1.96. z to alpha square will be 3.84. T is the prevalence or proportion of, which usually comes from the previous studies or from the pilot study. Q is given by 100 minus p and D is the allowable error or precision. Here, D can be either absolute or relative. Absolute means if it is five percentage means we will substitute directly this five percentage. 10 percentage relative means we take 10 percentage of the prevalence. 10 percentage of 50 percentage prevalence means five percentage. So, here is one example. Previous study, the p was identified as 60 percentage. So, then q will be 40. Here, it is the relative precision that is 20 percent relative to 60 percentage. Then the calculated sample size, when we substitute in the formula, it will be 65. So, the formula is 3.84 into pq divided by d square. If we increase the value of precision, then we get decreased sample size.