standard deviation

gte793n · Posted: Tue Sep 04, 2007 5:26 pm Post subject: standard deviation

standard deviation always gets me...

If a certain sample of data has a mean of 20.0 and a standard deviation of 3.0, which of the following values is more than 2.5 standard deviations from the mean?

a) 12.0
b) 13.5
c) 17.0
d) 23.5
e) 26.5

the answer: A

I have no idea what the question is asking..

source: OG

Thank you in advance.. Smile

agps · Posted: Wed Sep 05, 2007 2:59 am Post subject:

mean = 20
deviation =3

more than 2.5 deviations from mean (3*2.5 = 7.5, because 1 deviation is 3) any number farther than 7.5 from 20

only possible answer is A.

ri2007 · Posted: Wed Sep 05, 2007 3:27 pm Post subject:

Hey gte793n

Standard Deviation is really a simple concept

Think of the mean as the centre. SD is the distance from the mean.

Stastically it just denotes the normal deviation or the variation of the values from the mean or the centre value.

Hope this helps!!!

gte793n · Posted: Wed Sep 05, 2007 4:56 pm Post subject:

thanks for your help guys!