Question

what does x nomial mean in the % inaccuracy formula in (d)= ((xbar-xnominal)/xnominal)*100

Answer 1

which chapter is this from

Answer 2

It's a lab.

Answer 3

\[(d)=\frac{ xbar-x _{nominal} }{x _{nominal}}\]

Answer 4

Is the formula. xbar is an x with a line over it. It represents average I think.

Answer 5

@mathmat33 any ideas? what xnominal is?

Answer 6

@mathmath333 typed that wrong oops

Answer 7

\(\large\tt \color{black}{ ~accuracy~formula=\dfrac{x-y}{y}}\)
this i gor

Answer 8

not sure

Answer 9

xbar is average or mean of some sort. x nominal though. I do not know

Answer 10

@satellite73 test 1

Answer 11

http://en.wiktionary.org/wiki/ordinal_variable

Answer 12

Would this be the data I collected then?

Answer 13

i dun have any idea mate..i just googled it and this is wat i found X=nominal or ordinal variable, Y=nominal or ordinal variable

Answer 14

If it helps, the fill in the blank area states: Systematic Error % Innaccuracy d.

Answer 15

m sorry mate i have no idea...

Answer 16

But there only seems to be 1 space, so it can't be 1 calculation for every value I obtained from the lab, its 1 calculation for each volume measured.

Answer 17

anyone else have any ideas?

Answer 18

@Passion567 @surd @cj49 @mathmath333 @satellite74 anyone have any idea?

Answer 19

@UnkleRhaukus you there?

Answer 20

is xbar the average of values or true value

and xnominal is some indivual value

Answer 21

I think xbar is the average value. I do have an actual volume, but there are multiple, so I don't think they would work for a singular answer

Answer 22

u can post screenshot of question or theory

Answer 23

Er. IT will be loud, and everyone is sleeping.

Answer 24

Pag. 36 and forwards

Answer 25

actually, pg. 3 to 5.

Answer 26

That's the entire thing I'm working on.

Answer 27

For Table 1 there, I'm using the blue pipette.

Answer 28

ok so what are your volumes

Answer 29

I have 3 different groupings.

Volume measured at: 1000 microlitres.
998.7
1001
999.0
1003
1003.7
1002
1001
1003
1003
1003

Volume measured at: 500 microlitres
492.3
504.3
500.8
500.7
498.8
500.0
500.2
502.9
500.8
500.3
5001.3

Volume measured at: 100 microlitres
101.5
102.4
101.7
91.3
101.3
101.5
102.4
102.0
102.9
103.1

They are the actual volumes. not the measured volumes from the experiment.

Answer 30

Here's the excel document I've been using to assist in calculations.

Answer 31

i think for the first data set in the .xlsx file

xnominal is 1000, whereas xbar is 1001.8

Answer 32

Why do you think xnominal is 1000?

Answer 33

nominal means the thing to were aiming for,

Answer 34

you were aiming for 1000uL each time, but the average was 1001.8

Answer 35

Ah, that makes sense now!

I might ask this later, but are you good in determining sources of errors for chemistry too?I'll probably not get around to asking that though because I'll be doing the calculations.

Answer 36

d = ((1.8)/1000)*100%
= 1.8/10 %
=0.18%

a very small inaccuracy

Answer 37

hmm i could try with sources of error, but i haven't studied chem in a while
(i'm doing physics) , the sources of error usually depend on laboratory method the practical side of chem rater than the theoretical side.

Answer 38

Did you measure the temperatures/pressure of the liquid/room

Answer 39

Yes, I have those recorded.

Answer 40

I have an systematic error of 0.99%. Isn't that kinda of large, at least for these standards? I compared it with the given values.

Answer 41

Temperatre: 24 degree celsisu. pressure is 987 mb/hPa

Answer 42

I used that to approximate my value from Table 3 for the actual volume calculation (at 1.0037)

Answer 43

I'm not sure what standards you are following but 99.01% systematic accuracy sound pretty good to me

Answer 44

no no its inaccuracy. This is for the final data set, at a volume of 100 microlitres measured.

Answer 45

I'm sure i did a lot of significiant figure errors here though.

Answer 46

accuracy = 1 - inaccuracy

Answer 47

Well, I used the correct formula, according to the manual. I'm sorry, I'm extremely hungry right now, and must make food for myself.

Answer 48

well, my food is cooking now.

Answer 49

My only problem now is significant digits and sources of errors.

Answer 50

4) Calculate the Standard Deviation (SD or s); click on cell B12 and enter the Label ‘STDEV’, click on cell B13 and in the formula bar enter =STDEV(A8:A10), or use the insert function method. This will calculate the standard deviation for the three sample concentration. Next, ensure that you report correct number of significant figures for Cells A13 and B13, using one or two significant figures for the SD. (The Mean should not have more significant figures then is indicated by standard deviation. For example if the mean value reads 25.6778 and the SD is 0.246, then the result should be reported as 25.68 ± 0.25 or 25.7 ± 0.2. If your result indicates that the number of decimal places needs to be adjusted then select Format ⇒Cells ⇒Number and select the appropriate number of decimal places for the cell, or click on the tool bar icons that show a small arrow beside decimal zeroes to increase or decrease the number of decimal places displayed.
*NOTE: When reporting your experimental results you must always report the correct number of significant figures in your mean, SD and 95% CI. Marks will be deducted if incorrect significant figures are reported

Answer 51

Yeah, I've been setting, and then resetting hte significant figures. I've thankfully finished the excel portion, its just hte micropippetor section im still working n.

Answer 52

Oh, thanks for reminding me, I must print the second half of this work.

Answer 53

for errors,i have mechanical errors, as micropippetors do degrade over time. any other ideas?

Answer 54

gotta go. seeyall

Answer 55

They tell you (under calibration)

Calibration should be carried out at three volumes:
nominal, 50% and the smallest volume. For example, for 1000 mL pipette, calibration
should be done at 1000, 500 and 100 mL (see Table 1 below for the calibration volumes for
each pipette).


the "nominal" in \( x_{nominal} \) indicates the measured volume of the full pipette
e.g. the value you measure when you start will a full 1000 mL


Also, \( \bar{x} \) is the average of the x measurements.