Help with Math???

[mynameismatt]

I need help with my Math assignment on statistics.

Here is the question:

The weights of 10,000 women athletes were recorded and it was found they were normally distributed with a mean weight of 55kg and a standard deviation of 5kg. How many of these athletes weighed less than 45kg?

How many weighed more than 50kg?


I don't understand standard deviation can someone please explain????

 

[RossGr]

60% of all samples (observations) fall within 1 std. Dev. of the mean. This is of course for a perfect normal distribution. I do not have the % for 2 and 3 std. Dev. on top of my head. This info should be available to you. Do some reading.

As for your problem, I would need to sit with pensil and paper and perhaps cousult a stat book to get it right. Hope you will give it an effort.

 

[Relf Lauren]

<< I need help with my Math assignment on statistics.

Here is the question:

The weights of 10,000 women athletes were recorded and it was found they were normally distributed with a mean weight of 55kg and a standard deviation of 5kg. How many of these athletes weighed less than 45kg?

How many weighed more than 50kg?

I don't understand standard deviation can someone please explain???? >>



Ok, when you do std. dev. questions, always try to remember the graph.....just remember the mean is the &quot;number in the middle&quot;, and the &quot;target&quot; is the number you are working with...in your case, the mean is 55, which means the intersection of the x and y axis is 55.....you want to know how many weigh more than 50?...well, 50 is smaller than 55, so it would appear on the left hand side of the graph.....in order to calculate the percentages, you have to find out the standard score...you do this by subtracting the mean from the number, and then dividing by the std. dev......(in your case, the std. score would be (-1) for the 50kg....now, you have to have a table to use to find out the area under the graph when the point on the x axis equals negative one.....you do this, and find out the percentage from the y-axis to that point...since you are trying to find out how many weighed more than 50, you want all points from z to positive infinite....to do this, take the area under the normal dist. graph and add 50% to it.....

Repeat the same for 45kg...

Relf Lauren

 

[Relf Lauren]

I just read over what I wrote.....you must be confused...if you need any help, just PM me....

This stuff is easy compared to other things we have to do


Relf Lauren

 

[mynameismatt]

Thanks for the help I think I got it.

I think this is right: 1500 Athletes weigh less than 45kg and 8350 weigh more than 50kg.