Lab Report Uncertainties

[ILM]

Can uncertainties (after a series of calculations) be high? And if can it reach 75%, even if the value is in %.

[dessskris]

Uncertainty or percentage error? I think uncertainties can be quite high (around 10%) especially if your apparatus are not precise enough. And I think percentage errors can be even higher (my Chem teacher told us that the current IB2 students' IA's percentage errors are somewhere around 50%) especially if your procedures are not good (causing systematic error) and moreover if you compare your experimental value with a wrong literature value.

I do not think your uncertainties can reach 70% though unless your variable values are too close to zero but then I think uncertainties could never be higher than 15% I am not sure though. Probably you made a calculation mistake.

[ILM]

Uncertainty or percentage error? I think uncertainties can be quite high (around 10%) especially if your apparatus are not precise enough. And I think percentage errors can be even higher (my Chem teacher told us that the current IB2 students' IA's percentage errors are somewhere around 50%) especially if your procedures are not good (causing systematic error) and moreover if you compare your experimental value with a wrong literature value.

I do not think your uncertainties can reach 70% though unless your variable values are too close to zero but then I think uncertainties could never be higher than 15% I am not sure though. Probably you made a calculation mistake.

it was not not higher than 10%, but after a series of calculations 10 % changed to 20%, then to 30%. so is it possible to be that after series of calculations.

[dessskris]

Nah it's impossible. You must have calculated the uncertainties wrongly. Can you describe briefly what you did (multiplying this and that, substracting this from that, etc) and how you calculate the uncertainties?

[ILM]

i wanted to find the side length of the uncolored cube, so i subtracte side of the length (±5%) from diffusion depth of (10%) so my total uncertainity is (15%), then i want to find the volume of that, so the uncertainty is multiplied by three so it is 45%. then i subtract that from the total volume (± 15%) so it is (60%) then divide that by total volume( ±15%) to find the percentage of the uncolored part, so it is 75%.

[dessskris]

Did you use a ruler to measure the side length? Are you sure the unc is 5%? What's the absolute unc and what's the side length?

Did you measure the length of the coloured cube? Why didn't you measure the uncoloured cube's side length only instead so the unc will actually be smaller?? You can discuss this in CE btw..

Uncoloured cube's side length uncertainty = 15%

Uncoloured cube's volume uncertainty = 45%

If you subtract that from the total volume, you get the coloured cube's volume instead

Why did you divide that by the total volume?

% Uncoloured part should not have an uncertainty, I guess..or if there should be one, it should be unc of total volume + unc of uncoloured cube's volume, which is 15%+45%. So that's 60% only

But still!! That's a ridiculous result

[ILM]

I put that in my CE, but now iam editing the report, and it seems as you said 'ridiculous', but it seems logical if you look to calculation. I will not put any uncertainities for the percentage.