Given that the researcher wants to be sure the mean difference in the change in hemoglobin levels has a margin of error no more than 0.2 g/dL and the difference in the stand deviation between the mean hemoglobin levels for the two forms of iron supplements used to treat anemia is 1.2 g/dL, what is the desired number of recruits for the study, assuming the individuals will participate in a crossover trial, if the study's attrition rate is expected to be .25?

Group of answer choices

n = 139

n = 186

n = 554

n = 55,320