The grades of 11 students from a ninth grade English class were sampled. 78, 91, 88, 87, 66, 90, 64, 71, 80, 72, 71

1. a)Determine the mean, median and mode of the sample. (1 mark)
2. b)Determine the variance and standard deviation of the sample. (0.5 marks)
3. c)State the mathematical relationship between variance and standard deviation. (0.5 marks)