Significant figures

[Duarashid]

Hi, just wondering if you get marked down if you donot use the correct sig figs in your final answer.
If so, what are the rules?

Thankyou!

[jamonwindeyer]

Hi, just wondering if you get marked down if you donot use the correct sig figs in your final answer.
If so, what are the rules?

Thankyou!

I never applied a rule in my HSC, I just did what felt sensible (which was usually like 2 decimal places), or to something that let me express it in nm or km or whatever. I never lost marks on rounding, I think as long as you are sensible you are totally fine

The 'proper' rule though is that you give the same number of significant questions as the least you are given in the question (since this represents the variance in your input data, and your output data should suggest a similar variance)

[jazcstuart]

I don't know about physics, but for chemistry there is one mark allocated in the whole exam for correct rounding, but we don't know which question it will be. So if it's the same for physics, you could only lose one mark for the whole exam, however the downside is that you could round to the correct sig figs in all your answers except the one where the mark is allocated, and still lose the mark.
So I would say definitely try to round to the correct sig figs for every question if you can 

[Duarashid]

Okay! Thankyou!

I just realised that most times the least significant figures it’s usually 1 sig fig I.e. 9 x10^3 or something is the smallest value you use to get your answer. But if your answer is something like: 3.4556 you wouldn’t want to round to 3, it would make more sense to round to 3.5 right? What would you do in this situation?


Mod Edit: Merged posts

[jazcstuart]

Okay! Thankyou!

I just realised that most times the least significant figures it’s usually 1 sig fig I.e. 9 x10^3 or something is the smallest value you use to get your answer. But if your answer is something like: 3.4556 you wouldn’t want to round to 3, it would make more sense to round to 3.5 right? What would you do in this situation?


Mod Edit: Merged posts

I'm not sure sorry, I know in chemistry most values they give you to use in calculations are to 3 or 4 sig figs. I think if they only gave you 1 sig fig in the given values they would not be testing rounding for that question, but do whatever you think is best.

[zhudiac]

Okay! Thankyou!

I just realised that most times the least significant figures it’s usually 1 sig fig I.e. 9 x10^3 or something is the smallest value you use to get your answer. But if your answer is something like: 3.4556 you wouldn’t want to round to 3, it would make more sense to round to 3.5 right? What would you do in this situation?


Mod Edit: Merged posts

Hi,

In that case, I think it is best that you leave it in 1sf, just like Jamon said in his 'proper' rule- which you should follow just to be safe. Make sure when you're rounding always write theequality sign, and write the number of significant figures so that the marker won't think you did it by chance.

Also, say if you are doing for example double slit questions, and you are using the equation where m = 0, 1, 2, 3... In this case, as the value of 'm' is an integer, it is given to infinite significant figures, and so for rounding go by the next lowest significant figures.

[rh45_21]

Yes you will get marked down, if its mentioned, it will cost you a mark. Its a good habit to always check for that in questions so you can correct the answer accordingly.

[stella_atarnotes]

I think the way chem and phys works is that out of the entire HSC paper there is one question where there will be a mark allocated for significant figures. They don't tell you which one so it would be hit and miss if you don't always round to the correct significant figures. Make sure you are rounding to the lowest significant figure in the question. I would stick to having at least 2 significant figures in my answers, on the off chance that the lowest is 1 significant figure. They usually don't allocate a significant figure mark for questions where the lowest significant figure is 1.