Paired student's t - test: Comparing means (+-SD) in paired data.(in same group of individuals before and after an intervention) Example: Mean serum albumin level of dengue patients before treatment was 3.6 g/dL and after treatment was 3.2 g/dL; comparison of mean level can be done by Paired student's t - test. Unpaired student's t - test comparing means (+-SD) in two different group of individuals. Example: Mean HB level of anemia patients was 9.6 g/dL and those of hookworm patients was 7.2 g/dL; comparison of mean levels can be done by Unpaired student's t - test. In the given question, researcher wants to compare mean weight before and after an intervention. So, paired student's t - test will be most appropriate statistical test of significance.