A researcher collected the following sets of data. For each, indicate the measure of central tendency she should compute:

(a) The following IQ scores: 60, 72, 63, 83, 68, 74, 90, 86, 74, and 80;

(b) The following error scores: 10,15, 18,15, 14, 13,42, 15, 12,14, and 42;

(c) The following blood types: A—, A—, O, A+, AB —, A+, O, O, O, and AB +;

(d) The following grades: B, D, C, A, B, F, C, B, C, D, and D.