
Advanced Statistics Advanced Probability and Statistics Math Forum 
 LinkBack  Thread Tools  Display Modes 
May 13th, 2012, 05:46 AM  #1 
Newbie Joined: May 2011 Posts: 28 Thanks: 0  probablity in interval
Hello, Could you help me with this: Four speedmeters measured these values: 191, 199, 196 and 194 km/h. Standart deviation is 2 km/h (we can consider normal distribution). There are no errors in the measurements. What is the probability that speed is in interval (193, 195) ? thanks 
May 13th, 2012, 09:16 AM  #2 
Member Joined: Nov 2009 Posts: 90 Thanks: 0  Re: probablity in interval
Hello token22, According to this video lecture, the standard error of the mean (SEM) is 1/2. http://www.youtube.com/watch?v=J1twbrHel3o So 193 is 4 SEM from the sample mean. Using another video lecture as guidance, this should make your probability close to (just a tiny bit smaller than) 50%. http://www.youtube.com/watch?v=bekNKJoxYbQ Now you're gonna have to confirm this, because I'm quite sloppy. Let us know how it goes. 
May 13th, 2012, 12:21 PM  #3 
Newbie Joined: May 2011 Posts: 28 Thanks: 0  Re: probablity in interval
Oh i forgot to those youtube demonstration videos, anyway I got 0,4772 by video you sent, so it could be fine.

May 13th, 2012, 01:52 PM  #4 
Member Joined: Nov 2009 Posts: 90 Thanks: 0  Re: probablity in interval
Oh, that's right. SEM = s/(n^.5) = 2/(4^.5) = 1 So 0.4772 is right. Yeah, Mr Khan is awesome! 

Tags 
interval, probablity 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Probablity  DenmansDinner  Algebra  0  January 17th, 2012 09:13 PM 
Calculate probablity  neo  Algebra  3  December 16th, 2011 09:14 PM 
Probablity !!!! Confusing  daivinhtran  Algebra  4  June 11th, 2011 11:49 PM 
PRobablity  daivinhtran  Algebra  4  June 11th, 2011 07:52 PM 
PRobablity  daivinhtran  Algebra  1  June 11th, 2011 07:07 PM 