# Thread: statistic 2 help pls

1. ## statistic 2 help pls

Hi Everyone,

I am new to the forum and really need so help before I have a test tomorrow. I have been going over my book and working through the problems but I am stuck on this problem. Would someone please help me? thank you very much for your time

From a study
average height of men =68in sd=2.7inch
average forearm length=18in sd 1inch r=0.80

a) what percentage of men have forearms which are 18 inches long to the nearest inch? for this problem I figured out 38%

b) of the men who are 68inches tall, what percentage have forearms which are 18 inches long to the nearest inch?

I know that the nearest inch refers to 17.5 and 18.5 and the answer in the back of the book is 60% however, I do not know how they solve the problem to get 60%

2. Originally Posted by pinksapphire168
Hi Everyone,

I am new to the forum and really need so help before I have a test tomorrow. I have been going over my book and working through the problems but I am stuck on this problem. Would someone please help me? thank you very much for your time

From a study
average height of men =68in sd=2.7inch
average forearm length=18in sd 1inch r=0.80

a) what percentage of men have forearms which are 18 inches long to the nearest inch? for this problem I figured out 38%

b) of the men who are 68inches tall, what percentage have forearms which are 18 inches long to the nearest inch?

I know that the nearest inch refers to 17.5 and 18.5 and the answer in the back of the book is 60% however, I do not know how they solve the problem to get 60%
Let us determine how many standard deviations we moved to the right. Let $z$ represent that number. Then, $\mu+z\sigma =19.5$ since we know the values of these substitute them inside the equation,
$18+2.7z=18.5$ solving we get $z\approx .18$. Looking up this value on the distribution table we find that $\approx .071$ That tells us that approximately 7.1% are above 18 and below 18.5. Thus, since everything is in symettry over here the same applies to above 17.5 and below 18 is also 7.1%. Thus, in total we have approximately 14.2%.
The table which was used can be found at
http://www.statsoft.com/textbook/sttable.html