SLC5/03 Calc Standard Deviation help needed

[TerryRWood 0]

Hey Guys.... Looking for alternative ways of calculating STD DEV since the SLC5/03 does not have that it in it's instruction set. I know how to calculate it... I'm just looking to pick your brains... Everyone has a different approach. For those who don't know how to calculate it, there are 2 ways.... Deviation method for calculating standard deviation Consider the observations 8,25,7,5,8,3,10,12,9. First, calculate the mean and determine N. Remember, the mean is the sum of scores divided by N where N is the number of scores. Therefore, the mean = (8+25+7+5+8+3+10+12+9) / 9 or 9.67 Then, calculate the standard deviation as illustrated below. Score__ Mean____ Deviation__ *SquaredDeviation 8_______9.67_____ -1.67________ 2.79 25______ 9.67____+15.33______ 235.01 7_______ 9.67____ -2.67________ 7.13 5_______ 9.67____ -4.67_______ 21.81 8_______ 9.67____ -1.67________ 2.79 3_______ 9.67____ -6.67_______ 44.49 10______ 9.67__ __+.33_________ .11 12 ______9.67___ +2.33________ 5.43 9 _______9.67_____ -.67_________ .45 Sum of squared dev = 320.01*Deviation = Score - Mean Standard Deviation = Square root(sum of squared deviations / (N-1) = Square root(320.01/(9-1)) = Square root(40) = 6.32 Raw score method for calculating standard deviation Again, consider the observations 8,25,7,5,8,3,10,12,9. First, square each of the scores. Determine N, which is the number of scores. Compute the sum of X and the sum of X-squared. Then, calculate the standard deviation as illustrated below. Score_______ X2 8___________ 64 25_________ 625 7___________ 49.................N=9 5___________ 25 8___________ 64................ Sum of X=87 3____________ 9 10_________ 100................ Sum of X2=1161 12__________144 9____________ 81 --------------------------- 87_________ 1161 Standard Deviation = square root[(sum of X2)-((sum of X)*(sum of X)/N)/(N-1)] = square root[(1161)-(87*87)/9)/(9-1)] = square root[(1161-(7569/9)/8)] = square root[(1161-841)/8] = square root[320/8] = square root[40] = 6.32 THANX TRW Edited 3 Oct 2006 by TerryRWood

[rpraveenkum 5]

Use CPT instruction avalible in the SLC 5/03

[BobLfoot 302]

Are you wanting to do it for a Fixed N or will N cahnge each time you need to calculate STDEV?

[TerryRWood 0]

Hey Bob.... I need to do a Std Dev on a running average of at least 6 numbers. The application is to determine batch consistancy from a vibrating feeder, my numbers are final tare weights. I will evoke an action if the STD DEV exceeds 1.0 TRW