A researcher is interested in whether the phonics method of teaching reading is more or less effective than the sigh method, depending on the grade of the child. Twenty kids from each of three grades (Kindergarten, 1st, or 2nd) and from each of two teaching methods (phonics or sigh) completed a reading comprehension test. Is there a difference in reading comprehension by grade and teaching method? ___________ is the dependent variable in this problem. ___________ is the independent variable in this problem. ___________ is the appropriate statistical test to use for this