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#1
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probability density function
Can someone provide me with the formula for calculating the probaility
density function. Here is what I have, and what I need to get to: x value = 60 mean = 40 st dev = 15 thus: z score = 1.33 (using "standardize" function) Area under normal curve = 0.09 (1-NORMSDIST(1.33)) The value I am trying to get to is 0.16 (this is supposed to be the probability density function for the above value) Thanks Ariel |
#2
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probability density function
=EXP(-A1*A1/2)/SQRT(2*PI()) with your 1.33 in A1
-- David Biddulph "Ariel" wrote in message ... Can someone provide me with the formula for calculating the probaility density function. Here is what I have, and what I need to get to: x value = 60 mean = 40 st dev = 15 thus: z score = 1.33 (using "standardize" function) Area under normal curve = 0.09 (1-NORMSDIST(1.33)) The value I am trying to get to is 0.16 (this is supposed to be the probability density function for the above value) Thanks Ariel |
#3
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probability density function
"David Biddulph" wrote in message
... =EXP(-A1*A1/2)/SQRT(2*PI()) with your 1.33 in A1 .... and if you've been reading another thread regarding precedence of operators, you'll realise that you can't use =EXP(-A1^2/2)/SQRT(2*PI()) -- David Biddulph "Ariel" wrote in message ... Can someone provide me with the formula for calculating the probaility density function. Here is what I have, and what I need to get to: x value = 60 mean = 40 st dev = 15 thus: z score = 1.33 (using "standardize" function) Area under normal curve = 0.09 (1-NORMSDIST(1.33)) The value I am trying to get to is 0.16 (this is supposed to be the probability density function for the above value) Thanks Ariel |
#4
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probability density function
The simplest way is
=NORMDIST(A3,B3,C3,FALSE) which avoids issues of operator precedence. Note however that the value of the pdf is 0.011, not 0.16. Assuming that your values are rounded, the pdf for the unrounded values is no more than 0.012. Jerry "Ariel" wrote: Can someone provide me with the formula for calculating the probaility density function. Here is what I have, and what I need to get to: x value = 60 mean = 40 st dev = 15 thus: z score = 1.33 (using "standardize" function) Area under normal curve = 0.09 (1-NORMSDIST(1.33)) The value I am trying to get to is 0.16 (this is supposed to be the probability density function for the above value) Thanks Ariel |
#5
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probability density function
Hi David,
Thank you so much! This works perfectly! Ariel "David Biddulph" wrote: =EXP(-A1*A1/2)/SQRT(2*PI()) with your 1.33 in A1 -- David Biddulph "Ariel" wrote in message ... Can someone provide me with the formula for calculating the probaility density function. Here is what I have, and what I need to get to: x value = 60 mean = 40 st dev = 15 thus: z score = 1.33 (using "standardize" function) Area under normal curve = 0.09 (1-NORMSDIST(1.33)) The value I am trying to get to is 0.16 (this is supposed to be the probability density function for the above value) Thanks Ariel |
#6
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probability density function
It may give you the answer that you were looking for, but Jerry has pointed
out that it's the wrong answer. The pdf from the normalised distribution in my formula would need dividing by the standard deviation (15 in your case). Or more generally =EXP(-(X-MEAN*(X-MEAN)/(2*SDEV^2))/(SDEV*SQRT(2*PI())) -- David Biddulph "Ariel" wrote in message ... Hi David, Thank you so much! This works perfectly! Ariel "David Biddulph" wrote: =EXP(-A1*A1/2)/SQRT(2*PI()) with your 1.33 in A1 -- David Biddulph "Ariel" wrote in message ... Can someone provide me with the formula for calculating the probaility density function. Here is what I have, and what I need to get to: x value = 60 mean = 40 st dev = 15 thus: z score = 1.33 (using "standardize" function) Area under normal curve = 0.09 (1-NORMSDIST(1.33)) The value I am trying to get to is 0.16 (this is supposed to be the probability density function for the above value) Thanks Ariel |
#7
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probability density function
Hi Jerry and David,
The product must be 0.16, not 0.012 (this is a case from ther peer reviewed literature). Neither of these formulae provide that answer, however David's earlier formula in fact does provide that. I have another case below, also from the peer reviewed literatu x value = 6.50 mean = 5.21 st dev = 1.02 z score = 1.26 (using "standardize" function) Area under normal curve = 0.1038 (1-NORMSDIST(1.26)) Here the value I am trying to get to is 0.1804 (this is supposed to be the probability density function for the above value) Thanks Ariel "Jerry W. Lewis" wrote: The simplest way is =NORMDIST(A3,B3,C3,FALSE) which avoids issues of operator precedence. Note however that the value of the pdf is 0.011, not 0.16. Assuming that your values are rounded, the pdf for the unrounded values is no more than 0.012. Jerry "Ariel" wrote: Can someone provide me with the formula for calculating the probaility density function. Here is what I have, and what I need to get to: x value = 60 mean = 40 st dev = 15 thus: z score = 1.33 (using "standardize" function) Area under normal curve = 0.09 (1-NORMSDIST(1.33)) The value I am trying to get to is 0.16 (this is supposed to be the probability density function for the above value) Thanks Ariel |
#8
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probability density function
...from the peer reviewed literatu
Hi. You are using a normal mean of 0, and std of 1. =NORMDIST(1.33,0,1,FALSE) =NORMDIST(1.26,0,1,FALSE) These return your .16 & .18 However, you give mean = 40 st dev = 15 mean = 5.21 st dev = 1.02 -- HTH :) Dana DeLouis Windows XP & Office 2003 "Ariel" wrote in message ... Hi Jerry and David, The product must be 0.16, not 0.012 (this is a case from ther peer reviewed literature). Neither of these formulae provide that answer, however David's earlier formula in fact does provide that. I have another case below, also from the peer reviewed literatu x value = 6.50 mean = 5.21 st dev = 1.02 z score = 1.26 (using "standardize" function) Area under normal curve = 0.1038 (1-NORMSDIST(1.26)) Here the value I am trying to get to is 0.1804 (this is supposed to be the probability density function for the above value) Thanks Ariel "Jerry W. Lewis" wrote: The simplest way is =NORMDIST(A3,B3,C3,FALSE) which avoids issues of operator precedence. Note however that the value of the pdf is 0.011, not 0.16. Assuming that your values are rounded, the pdf for the unrounded values is no more than 0.012. Jerry "Ariel" wrote: Can someone provide me with the formula for calculating the probaility density function. Here is what I have, and what I need to get to: x value = 60 mean = 40 st dev = 15 thus: z score = 1.33 (using "standardize" function) Area under normal curve = 0.09 (1-NORMSDIST(1.33)) The value I am trying to get to is 0.16 (this is supposed to be the probability density function for the above value) Thanks Ariel |
#9
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probability density function
The pdf for an x value of 60 for a normal distribution of mean 40 and
standard deviation 15 is 0.0109 The value of 0.164 is the pdf of a normalised distribution (hence at an x value of 60/15 on a distribution of mean 40/15 and a standard deviation of 1). [I couldn't immediately get 0.1804 by an equivalent process for your second set of figures. The only way you get 0.1804 is by rounding the (x - mean)/sdev value to 3 significant figures, and hence you shouldn't quote the answer to four significant figures.] You need to be careful as to what quantity you want. -- David Biddulph "Ariel" wrote in message ... Hi Jerry and David, The product must be 0.16, not 0.012 (this is a case from ther peer reviewed literature). Neither of these formulae provide that answer, however David's earlier formula in fact does provide that. I have another case below, also from the peer reviewed literatu x value = 6.50 mean = 5.21 st dev = 1.02 z score = 1.26 (using "standardize" function) Area under normal curve = 0.1038 (1-NORMSDIST(1.26)) Here the value I am trying to get to is 0.1804 (this is supposed to be the probability density function for the above value) Thanks Ariel "Jerry W. Lewis" wrote: The simplest way is =NORMDIST(A3,B3,C3,FALSE) which avoids issues of operator precedence. Note however that the value of the pdf is 0.011, not 0.16. Assuming that your values are rounded, the pdf for the unrounded values is no more than 0.012. Jerry "Ariel" wrote: Can someone provide me with the formula for calculating the probaility density function. Here is what I have, and what I need to get to: x value = 60 mean = 40 st dev = 15 thus: z score = 1.33 (using "standardize" function) Area under normal curve = 0.09 (1-NORMSDIST(1.33)) The value I am trying to get to is 0.16 (this is supposed to be the probability density function for the above value) Thanks Ariel |
#10
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probability density function
Excellent!!! Thanks Dana.
"Dana DeLouis" wrote: ...from the peer reviewed literatu Hi. You are using a normal mean of 0, and std of 1. =NORMDIST(1.33,0,1,FALSE) =NORMDIST(1.26,0,1,FALSE) These return your .16 & .18 However, you give mean = 40 st dev = 15 mean = 5.21 st dev = 1.02 -- HTH :) Dana DeLouis Windows XP & Office 2003 "Ariel" wrote in message ... Hi Jerry and David, The product must be 0.16, not 0.012 (this is a case from ther peer reviewed literature). Neither of these formulae provide that answer, however David's earlier formula in fact does provide that. I have another case below, also from the peer reviewed literatu x value = 6.50 mean = 5.21 st dev = 1.02 z score = 1.26 (using "standardize" function) Area under normal curve = 0.1038 (1-NORMSDIST(1.26)) Here the value I am trying to get to is 0.1804 (this is supposed to be the probability density function for the above value) Thanks Ariel "Jerry W. Lewis" wrote: The simplest way is =NORMDIST(A3,B3,C3,FALSE) which avoids issues of operator precedence. Note however that the value of the pdf is 0.011, not 0.16. Assuming that your values are rounded, the pdf for the unrounded values is no more than 0.012. Jerry "Ariel" wrote: Can someone provide me with the formula for calculating the probaility density function. Here is what I have, and what I need to get to: x value = 60 mean = 40 st dev = 15 thus: z score = 1.33 (using "standardize" function) Area under normal curve = 0.09 (1-NORMSDIST(1.33)) The value I am trying to get to is 0.16 (this is supposed to be the probability density function for the above value) Thanks Ariel |
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