The average class size this semester in the business school of a particular university is 16 students with a standard deviation of 3.9 students. The z-score for a class with 21 students is .

1.28

Step-by-step explanation:

We are given;

Population mean; μ = 16

Population standard deviation; σ = 3.9

Sample mean; x' = 21

Formula for z-score is;

z = (x' - μ)/σ

z = (21 - 16)/3.9

z = 1.28

c. y = 1/4 x + 5

step-by-step explanation:

first, put the equation of the line on the graph into slope-intercept form

(y = mx + b):   y = -4x + 8

second, a perpendicular line has to have "an opposite/reciprocal slope" to the original slope. so, find the "m" value in your original equation (it's -4, right? )

original slope: m = -4   perpendicular slope: change the sign to its opposite and find the reciprocal ("flip" the number)

new slope is now positive (b/c the original slope was negative 4), and it's 1/4 (not the original slope of 4 or 4/1)

the answer is:

mean: 6

mad: 2.14