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## Homework Statement

In an ancient culture, the average male life span was 37.6 years, with a standard deviation of 4.8 years The average female life span was 41.2 years, with a standard deviation of 7.7 years. use the properties of the normal distribution to find the following:

a. What percentage of men died before age 30?

b. What percentage of women lived to an age of at least 50?

c. At what age is a female death at the same relative position in the distribution as a male death at age 35?

## Homework Equations

[tex]X'=s'z+\overline{X}[/tex]

using Standard Normal Distribution table to find percentile rank

## The Attempt at a Solution

Problem a a is clear for me, but I have a little doubt in b, because

I am confused about choosing between [tex]PR_{49.9}[/tex] or [tex]PR_{50}[/tex]? Percentile rank is defined as

**at**or

**below**. So, if it is said

**at least**, I have to choose lower number, but what is it? Is it 49.9; 49.99; 49.999; or... So that's why I think [tex]PR_{50}[/tex] is the best "hyprotika.wordpress.com"[/URL]

Problem c is just using z-score right? So I don't have to apply Normal Curve Equivalent here? Finding z-score for male rate, then using mean and standard deviaton for female rate, then that's the answer. Is it right?

Thanks for the answer. [PLAIN]"hyprotika.wordpress.com"[/URL]

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