B. Statistics plpette at both 100 and 1000 pl settings 1. Take the mean for each

Question

B. Statistics plpette at both 100 and 1000 pl settings 1. Take the mean for each group of ten readings. 2. Use the mean to calculate the standard deviation. nis Ldiation, add the dis 10), and cach set vary from the tandard deviation. This aumber represents how much the values in the group minus the mean. Divide this by the number of values (in your square root of that number. See the equation below: clate the standard deviation, add the square of cach value in case, it is 10), and take the 2(x-mean)?+ (mean).. 30-mean) # of samples in group Where X through Xio are the 10 replicate readings at one setting (sanm For example: 1. If your values for the 1000 1 setting were 998, 989, 1005, 1001, 1011, 993, 1014, 1002, 997, and 1009 l. The mean would be 1001.9. 2. When you subtract the mean from each value and square it, you would ge 3. When these numbers are added and divided by ten, you get 57.49. 81, 82.81,79.21, 146.41, .01,24.01, and 50.41 The square root of this number is 7.58. This would mean that as ing varied by 7.58 ul you were trying to pipette 1000 , the amount you were actually dispens- by dividing the 4. Calculate the % difference between the standard deviation and the mean value standard deviation by the expected value and multiplying by 100. × 100 % difference- standard deviation Mean % differences 7.58 x100-0.76% 1001.9

Explanation / Answer

1. when 10 values for 1000 µl are as follows-

998, 989, 1005, 1001, 1011, 993, 1014, 1002, 997, 1009

then the mean will be calculated as: 998+989+1005+1001+1011+993+1014+1002+ 997+1009/10= 1001.9

2.then subtract the mean value from each and square it-

(998-1000.9)= -3.9

3.9 X 3.9 = 15.21

similarly,

                (989-1000.9)= -12.9

12.9 X 12.9 = 166.41

(1005-1001.9)=3.1

3,1x3.1=9.61

in this way we get 10 values like

15.21, 166.41, 9.61, 0.81, 82.81, 79.21, 146.41, .01, 24.01, 50.41

mean of these values are

15.21+166.41+9.61+0.81+82.81+79.21+146.41+ .01+24.01+50.41/10 =574.9/10=57.49

square root of this = 7.58

as when we do a square of 7.58 or 7.58 X 7.58 = 57.49

4. thus % difference will be

standard deviation / mean X 100

or 7.58 / 1001.9 X 100= 0.76%

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