Chem Exam

[AAGlue]

Yeah since there was no space I wasn’t specific to the question about C4H.....oops I could barely fit explaining what that is AND how it helps to decide. 0/3 marks for me VCAA have mercy 

This is how VCAA makes exams hard
You don’t get marks because of bad formatting lol
I think you’ll get at least 1 mark though for writing something tho

[AAGlue]

What did you guys say when it asked to talk about comparing methane obtained from landfill compared  to natural gas?

Landfill - positive impact, burning CH4 into CO2 minimises impact of CH4 that was going to be released anyway from the landfill since CH4 is a more potent greenhouse gas than CO2
Natural gas - non-renewable fossil fuel -> exacerbates climate change

[99.95_goal]

No I got 0.73 bananas, because there’s less carbs, and cuz the energy value is smaller when you take away the fibre you need more bananas to get the 300 Kj
Wow what did I just write omg lol

Ok sorry gotcha now - wow that's really confusing actually

[AAGlue]

Ok sorry gotcha now - wow that's really confusing actually

Tbh they should put dietary fibre as a subgroup under carbohydrates, literally no one separates them in real life
VCAA put so many bad Qs in the exam today lol

[Isaac S]

In multiple choice, question 2, what did a larger sample size in an experiment improve? Validity, reliability, precision or uncertainty?

[RingoAC]

In multiple choice, question 2, what did a larger sample size in an experiment improve? Validity, reliability, precision or uncertainty?

reliability I reckon

[AAGlue]

reliability I reckon

I said validity... I feel like I'm right tho?

I think it would be reliability
Cuz even if you increase the sample space if the method sucks it still would be invalid
Reliability is like consistency so if you get more (precise) results that fit within the range you can say its more reliable

[Isaac S]

Rip. What other hard MC's were there

[keltingmeith]

In multiple choice, question 2, what did a larger sample size in an experiment improve? Validity, reliability, precision or uncertainty?

This is an interesting one - I would say that the correct answer is uncertainty, and here's why:

1. A larger sample size can improve validity - but if your larger selection still has the same sampling bias as your smaller sample size, then the experiment is just as invalid.

2. Reliability. See above. If you're still sampling the wrong kind of people, your results are just unreliable

3. Precision, is where it gets interesting... You see, in some sense, precision and uncertainty go hand in hand. I've opted for precision to be incorrect because past, individual experiments can be just as imprecise.

4. Uncertainty, however, is kind of an average of the precision - and uncertainty HAS to go down if you increase the number of experiments, even if the new tests are just as imprecise as the previous ones, because that's the nature of uncertainty - repeat results give you more confidence for them to keep repeating.

But this is a tricky one, and I wouldn't be surprised if VCAA has a different stance - I could reasonably see all of these being improved by an increase in sample size, so we'll just have to wait and see what VCAA says. And who knows, maybe they'll decide in hindsight that this was too ambiguous, and give multiple answers a mark (this has been done in the past, though I don't remember the exact question - just that it was in my specialist exam, back when I took the subject)

[AAGlue]

This is an interesting one - I would say that the correct answer is uncertainty, and here's why:

1. A larger sample size can improve validity - but if your larger selection still has the same sampling bias as your smaller sample size, then the experiment is just as invalid.

2. Reliability. See above. If you're still sampling the wrong kind of people, your results are just unreliable

3. Precision, is where it gets interesting... You see, in some sense, precision and uncertainty go hand in hand. I've opted for precision to be incorrect because past, individual experiments can be just as imprecise.

4. Uncertainty, however, is kind of an average of the precision - and uncertainty HAS to go down if you increase the number of experiments, even if the new tests are just as imprecise as the previous ones, because that's the nature of uncertainty - repeat results give you more confidence for them to keep repeating.

But this is a tricky one, and I wouldn't be surprised if VCAA has a different stance - I could reasonably see all of these being improved by an increase in sample size, so we'll just have to wait and see what VCAA says. And who knows, maybe they'll decide in hindsight that this was too ambiguous, and give multiple answers a mark (this has been done in the past, though I don't remember the exact question - just that it was in my specialist exam, back when I took the subject)

But tbh we didn’t even learn uncertainty in class lol
U4 AOS 3 was a complete mess  : D

[keltingmeith]

But tbh we didn’t even learn uncertainty in class lol
U4 AOS 3 was a complete mess  : D

I can imagine - and again, add that to a question that I would call ambiguous at best in the first place, I would not feel bad if you lost this one mark, and take solace in knowing they might allow multiple answers, anyway.

[AAGlue]

I can imagine - and again, add that to a question that I would call ambiguous at best in the first place, I would not feel bad if you lost this one mark, and take solace in knowing they might allow multiple answers, anyway.

Thank god, the MCQ this year was literally cursed

[zoharreznik]

33%

Might be just me but the delta T was 32.3-20 so I rounded it to 12 and got 35%. Would that be correct? (Considering that’s how significant figures work)

[Daza234]

This is an interesting one - I would say that the correct answer is uncertainty, and here's why:

1. A larger sample size can improve validity - but if your larger selection still has the same sampling bias as your smaller sample size, then the experiment is just as invalid.

2. Reliability. See above. If you're still sampling the wrong kind of people, your results are just unreliable

3. Precision, is where it gets interesting... You see, in some sense, precision and uncertainty go hand in hand. I've opted for precision to be incorrect because past, individual experiments can be just as imprecise.

4. Uncertainty, however, is kind of an average of the precision - and uncertainty HAS to go down if you increase the number of experiments, even if the new tests are just as imprecise as the previous ones, because that's the nature of uncertainty - repeat results give you more confidence for them to keep repeating.

But this is a tricky one, and I wouldn't be surprised if VCAA has a different stance - I could reasonably see all of these being improved by an increase in sample size, so we'll just have to wait and see what VCAA says. And who knows, maybe they'll decide in hindsight that this was too ambiguous, and give multiple answers a mark (this has been done in the past, though I don't remember the exact question - just that it was in my specialist exam, back when I took the subject)

I'm pretty sure the question asked which of the four would increase with a larger sample size. Uncertainty would decrease with a larger sample, so I don't think that was the correct option. The wording may be important. Reliability seems like the right one.

[zoharreznik]

I'm pretty sure the question asked which of the four would increase with a larger sample size. Uncertainty would decrease with a larger sample, so I don't think that was the correct option. The wording may be important. Reliability seems like the right one.

Yep I think that was how it was worded