What is the z-score of a value of 104.5, in a set with \$\mu\$ = 125 and \$\sigma\$ = 6.2?

x = 104.5 , \$\mu\$ = 125 , \$\sigma\$ = 6.2

z-score = \$\frac{x- \mu}{\sigma}\$

Put x = 104.5 in the formula

z-score = \$\frac{104.5- \mu}{\sigma}\$

Then substract the mean by substitution

z-score = \$\frac{104.5- 125}{\sigma}\$ = \$\frac{-20.5}{\sigma}\$

Divide the obtained value by standard deviation \$\sigma\$ = 6.2

z-score = \$\frac{-20.5}{6.2}\$

z-score at 104.5

-3.306

measured value 104.5 is less than mean 125

z-score is negative

Answer

C