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: A2, A2, O, A1, AB2, A1, O, O, O, and AB1; (d) the following grades: B, D, C, A, B, F, C, B, C, D, and D.