No. of Significant Figures & Decimal Places in Papers 1 & 2

[IB`NOT`ez]

I'm rather confused if its required by the IB, on penalty of losing marks, to always leave answers in 3 significant figures. Different sources tell me otherwise: a mark scheme from the old Maths SL syllabus (pre-2014) states that a -1 mark for inaccuracy be applied to the whole paper, once, if there is any instance of inappropriate significant figures in the answer. However, the mark schemes for the current syllabus are very vague regarding this, and I cannot interpret anything whatsoever. My Maths teacher is also rather unsure about the importance of significant figures, whereas DP coordinator says you can leave your answer to 99999 significant figures if you really want, especially for GDC-related answers in Paper 2, and there is no penalty whatsoever.

But also, what if there discrepancies in numbers for Paper 2 questions? For example, if the answer is 0.776, but my answer is 0.775, will I receive no marks for the final answer whatsoever, or only be applied a -1 mark for inaccuracy? The following is stated in the mark scheme for the May 2016 Paper 2 TZ1: 

10. 10  Accuracy of Answers

    Candidates should NO LONGER be penalized for an accuracy error (AP).

    If the level of accuracy is specified in the question, a mark will be allocated for giving the answer to the required accuracy. When this is not specified in the question, all numerical answers should be given exactly or correct to three significant figures. Please check work carefully for FT.

This is really confusing. I MUST give all numerical answers exactly or correct to 3 s.f. But if I don't, will I NOT be penalized, or will I STILL be penalized? Additionally, I'm wondering if there are differences in accuracy policies between Paper 1 and Paper 2. I'd like to think that significant figure inaccuracies will be less prevalent in Paper 1, therefore if the IB follows this line of thought, will penalties be harsher?

Hoping someone can help clarify this.

Thank you.

Edited April 23, 2017 by IB`ez

[kw0573]

It should be evident that you dont need significant figures on paper 1 since you will give exact answers. 

Markscheme means that now it's either yes or no (as opposed to yes, no by AP, no by wrong answer). Remember in IB and later in university, there is little benefit of the doubt on exams.

If correct answer is 0.77589... then markscheme says 0.776. You will be marked correct if you answer 0.776, 0.77589, 0.7755147 (which clearly rounds to the accepted answer) etc. You will be marked incorrect in general for 0.775, 0.774, 0.77549, 0.8, 0.78. (0.775 would be accepted if only 2 sig figs were required). The explanation is that more digits imply you get the answer to the required accuracy but fewer digits do not. As a result, you should use calculator memory to store answers in entirety in many-step calculation instead of reentering first few digits. Be extra prudent when dealing with sinuocidal, logarithmic and exponential functions.

[IB`NOT`ez]

46 minutes ago, kw0573 said:

It should be evident that you dont need significant figures on paper 1 since you will give exact answers. 

Markscheme means that now it's either yes or no (as opposed to yes, no by AP, no by wrong answer). Remember in IB and later in university, there is little benefit of the doubt on exams.

If correct answer is 0.77589... then markscheme says 0.776. You will be marked correct if you answer 0.776, 0.77589, 0.7755147 (which clearly rounds to the accepted answer) etc. You will be marked incorrect in general for 0.775, 0.774, 0.77549, 0.8, 0.78. (0.775 would be accepted if only 2 sig figs were required). The explanation is that more digits imply you get the answer to the required accuracy but fewer digits do not. As a result, you should use calculator memory to store answers in entirety in many-step calculation instead of reentering first few digits. Be extra prudent when dealing with sinuocidal, logarithmic and exponential functions.

Thank you for your response!

Therefore, leaving my answer in 0.776313123123123123123123 would still be acceptable for the complete marks right? With regards to a 0.775 though, I would still earn working marks, but only lose the final mark right?

[SC2Player]

From what my textbooks tell me, significant figures are (somewhat) important in IB exams.  They gave me some rules for significant figures.  I haven't checked the actual markschemes though - they'd probably give the most definitive answer on the use of significant figures in IB exams.  If what my teachers tell me are right, though, messing up significant figures will result in you losing a maximum of exactly 1 mark (apparently making 1 error and 100 errors with significant figures are more or less the same now), so I'd advise you brush up on everything else first.  

[IB`NOT`ez]

1 hour ago, SC2Player said:

From what my textbooks tell me, significant figures are (somewhat) important in IB exams.  They gave me some rules for significant figures.  I haven't checked the actual markschemes though - they'd probably give the most definitive answer on the use of significant figures in IB exams.  If what my teachers tell me are right, though, messing up significant figures will result in you losing a maximum of exactly 1 mark (apparently making 1 error and 100 errors with significant figures are more or less the same now), so I'd advise you brush up on everything else first.  

With only a week left before exams, there isn't much to brush up on anymore – was hoping to refine my exam approach to the best of my ability and avoid any easily avoidable mistakes. 

From your sources, is it losing one mark per question you screwed up significant figures for, or -1 mark per the whole paper? The latter I think, is no longer the case for Maths SL and HL of the 2014 syllabus. 

Edited April 23, 2017 by IB`ez

[kw0573]

10 hours ago, IB`ez said:

Thank you for your response!

Therefore, leaving my answer in 0.776313123123123123123123 would still be acceptable for the complete marks right? With regards to a 0.775 though, I would still earn working marks, but only lose the final mark right?

If the accepted answer is 0.776, then what you are given is accepted. I believe it's -1 per instance of not having correct to 3 sig fig. 

[SC2Player]

After re-checking the markschemes for past papers involving IB HL Maths (which say the same thing), I have to say I was wrong before.  My interpretation is that rounding errors aren't going to be penalized as long as it's not wildly inaccurate.  

With that said, however, my interpretation may be wrong, and I don't know how applicable is this towards Maths SL.  My maths teacher also emphasizes the importance of rounding to 3 significant figures.  It might be best to just give exact answers whenever possible, as this avoids the issue of rounding, and only give rounded answers whenever it's basically impossible to give an exact answer (e.g. finding probabilities involving normal distributions).  

Edited April 24, 2017 by SC2Player

[Aanya4]

What about Ibdp physics?? What are the sf requirements? Also how to go about rounding off 1.805 to 2 dp.... according to my textbook it should be 1.80 (because 0 is an even number; tb says dispose 5 if even no. precedes it and rest of no. is ans.) but don't we always round up if last digit ≥ 5?? Kindly clarify..

Edited September 8, 2020 by Aanya4