In a certain​ city, the average​ 20- to​ 29-year old man is 72.5 inches​ tall, with a standard deviation of 3.2 ​inches, while the average​ 20- to​ 29-year old woman is 64.5 inches​ tall, with a standard deviation of 3.8 inches. Who is relatively​ taller, a​ 75-inch man or a​ 70-inch woman?

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Answer:

​ 70-inch woman is taller.

Step-by-step explanation:

Given data:

For men

age group = 20 - 29 year

Height = 72.5 inches

standard deviation = 3.2 inches

For women

age group = 20 - 29 year

Height = 64.5 inches

standard deviation = 3.8 inches

To find:

who is taller?  a​ 75-inch man or a​ 70-inch woman?

To find that, firstly we find z- score for each gender.

Solve:

Z-score=(x-μ)/σ

where:

μ=mean

σ=std deviation

Z(men) = (75-72.5)/3.2

            = 0.781

Z(women) = (70-64.5)/3.8

               = 1.447

From the above, the z-score for the woman is relatively larger than that of the man, this means that the woman is taller.

We can use z scores to see which of the given values are relatively higher(taller) relative to their groups.

The 70-inch woman is relatively taller in women's group than 75-inch man in men's group (specified group).

How to get the z scores?

If we've got a normal distribution, then we can convert it to standard normal distribution and its values will give us the z score.

If we have [tex]X \sim N(\mu, \sigma)[/tex] then it can be converted to standard normal distribution as

[tex]Z = \dfrac{X - \mu}{\sigma}, \\\\Z \sim N(0,1)[/tex]

Using the above method to get the z scores for both the 75 inch man and 70 inch woman

Let X tracks height of men and Y tracks height of women, then we have:

[tex]X \sim N(72.5, 3.2)\\Y \sim N(64.5, 3.8)[/tex]

Converting them to standard deviation and getting the z score:

For 75 inch man:

[tex]Z = \dfrac{X - 72.5}{3.2} = \dfrac{75 - 72.5}{3.2} = \dfrac{2.5}{3.2} = 0.78125[/tex]

For 70 inch woman:

[tex]Z = \dfrac{Y - 64.5}{3.8} = \dfrac{70 - 64.5}{3.8} = \dfrac{5.2}{3.8} = 1.368[/tex]

Thus,  

The 70-inch woman is relatively taller in women's group than 75-inch man in men's group (specified group).

Learn more about standard normal distribution here:

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