hours/ week.......12....32.....35.....38.....42 T=159

# of employees....1.....5.......7.......8......5 T=26

(x-mu)............-23.8..-3.8..-0.8...2.2....6.2

.......566.44...14.44...0.64...4.84...38.44 T=544.80

determine the mean, variance, and standard deviation for the nurse's hours

the mean is 35.8...

I need to know which equations to use for variance and standard deviation...

can someone show me the eq. needed to find each and (if there is) the sequence to find them?