Suppose the random variable x is best described by a normal distribution with μ=30 and σ=4. Find the z-score that corresponds to each of the following x values:

a.x=20b.x=30c.x=2.75d.x=15e.x=35f.x=25

Short Answer

Expert verified
  1. z = -2.5
  2. z = 0
  3. z = -6.1825
  4. z = -3.75
  5. z = 1.25
  6. z = -1.25

Step by step solution

01

Given information

Here, x is a random variable that is normally distributed withμ=30 andσ=4

02

Finding the z-score when x=20

a.

When x = 20, the z score will be -

z=x-μσ=20-3014=-1014=-2.5

Therefore, the z-score forx = 20is -2.5.

03

Finding the z-score when x=30

b.

When x=30, the z score will be -

z=x-μσ=30-304=04=0

Therefore, the z-score for x = 30 is 0.

04

Finding the z-score when x=2.75

c.

When x=2.75, the z score will be -

z=x-μσ=2.75-304=-27.254=-6.8125

Therefore, the z-score for x=2.75 is -6.8125.

05

Finding the z-score when x=15

d.

When x=15, the z score will be -

z=x-μσ=15-304=-154=-3.75

Therefore, the z-score for x=15 is -3.75.

06

Finding the z-score when x=35

e.

When x=35, the z score will be -

z=x-μσ=35-304=54=1.25

Therefore, the z-score for x=35 is 1.25.

07

Finding the z-score when x=25

f.

When x=25, the z score will be -

z=x-μσ=25-304=-54=-1.25

Therefore, the z-score for x=25 is -1.25.

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