Question

Suppose students voluntarily take a remedial reading course. Who might be likely to leave the study before the posttest? What effect is this likely to have on the data analysis?

Answer 1

Answer,

Students who are already fluent in reading may likely drop out of the experiment before post test as they would have already benefitted from the remedial course and may feel less motivated to continue with the treatment condition.

Dropping out of participants would mean that the sample size would decrease which would affect the mean and thus eventually lead to erroneous conclusions as it can lead to a finding of a significant difference where in actuality there may be no difference as the final sample would not remain a random sample which included representation of all the elements of the population of students as it the sample statistics would have excluded the students who were already fluent in reading skills and one cannot traces the efficacy of the remedial programme on them.