the formula for standard deviation of a sample is: s equals square root of fraction numerator 1 over denominator n minus 1 end fraction sum from i equals 1 to n of open parentheses x subscript i minus x with bar on top close parentheses squared end root select the true statement for the following data set that has a mean of 5: 2, 4, 4, 4, 5, 5, 5, 7, 9
a) the variance is 8 and the standard deviation is 0.
b) the variance is 2 and the standard deviation is 4.
c) the variance is 4 and the standard deviation is 2.
d) the variance is 3 and the standard deviation is 1.