Maths Questions - N...
 

  You don't need to be an 'investor' to invest in Singletrack: 6 days left: 95% of target - Find out more

[Closed] Maths Questions - Normal Distribution

7 Posts
5 Users
0 Reactions
44 Views
Posts: 27
Free Member
Topic starter
 

I have a maximum and a minimum, can I calculate the theoretical lower quartile, median and upper quartile based on only this for a normal distribution?


 
Posted : 12/02/2010 11:33 am
Posts: 0
Free Member
 

I think you'll need the standard deviation for your distribution as well.


 
Posted : 12/02/2010 11:36 am
Posts: 0
Free Member
 

No, of course not. How on earth do you know how much of an outlier your max and min are?


 
Posted : 12/02/2010 11:39 am
Posts: 0
Full Member
 

as above, you ned the standard deviation.


 
Posted : 12/02/2010 11:40 am
Posts: 27
Free Member
Topic starter
 

ok, what if i can assume a standard normal distribution with a variance of 1?


 
Posted : 12/02/2010 11:54 am
Posts: 27
Free Member
Topic starter
 

it's ok, I've worked it out
I can use the =NORMSINV() formula in Excel


 
Posted : 12/02/2010 12:29 pm
Posts: 943
Free Member
 

to randomly sample from a Normal

= NORMINV(RAND(),mean,stdev)

to calc P(X<=x)

=NORMDIST(x,mean,stdev,TRUE)

to calc a value of x given a prob.

= NORMINV(p, mean, stdev)

where p is the area to the left of the unknown x value

The Normal dist is unbounded so has no min or max, theoretically speaking


 
Posted : 12/02/2010 1:00 pm
Posts: 943
Free Member
 

replace NORMINV with NORMSINV

and NORMDIST with NORMSDIST

if you want standard normal, rather than the original data


 
Posted : 12/02/2010 1:01 pm

6 DAYS LEFT
We are currently at 95% of our target!