Common Mistakes

[studyingg]

I think we can all agree stupid mistakes are the bane of every FM student's existence 

So, do you guys wanna quickly start this thread of common FM mistakes so that we can all share common mistakes we make, and become conscious about them before the exam (perhaps even make a checklist to add into our bound references).

I'll start
Data Analysis:
-Not checking whether the scale is in percentage frequency or just normal frequency

-If something has been rescaled to be 'in thousands', you have to times your answer by one thousand (for example a residual of -3 becomes -3000)

-Not answering questions (by yes/or no) when they say 'is there an association?', and just explaining straight away
-assuming that my answer for part b is related to part a (it usually isn't)

Financial:
-Mistakingly giving the answer for interest paid during a particular time period, when the question wants the interest paid over a time period (and vice versa)

-Misreading the question, when it asks for the percentage rate of depreciation/interest for linear growth or decay, and giving my answer as the amount of depreciation (and vice versa)

-lol forgetting to round to the nearest dollar

Matrices:
-not being specific enough when interpreting a matrix (for example the sum of row three represents [person's] number of friends --- should actually be:  the sum of row three represents [person's] total number of friends out of the group of [number of people)
-Not showing two calculations for long term matrices
-not giving an answer in integer solutions when it does not make sense for it to be a decimal

Graphs:
-sometimes they'll label a coordinate outside of the feasible region for a linear programing question in multiple choice, and I will mistakenly assume it is a corner point.


I'll come back to add more

[Lear]

Financial, when asked to use recurrence relation or write a recurrence relation YOU MUST MUST Write the initial term first.

This is WRONG
Vn+1=0.5Vn where V0 = 1000

This is correct
V0=1000, Vn+1=0.5Vn


Stupid thing that examiners are fussy about that textbooks don’t teach (and often do incorrect themselves)

[studyingg]

Financial, when asked to use recurrence relation or write a recurrence relation YOU MUST MUST Write the initial term first.

This is WRONG
Vn+1=0.5Vn where V0 = 1000

This is correct
V0=1000, Vn+1=0.5Vn


Stupid thing that examiners are fussy about that textbooks don’t teach (and often do incorrect themselves)

Omg yes! Something also related to this
if it asks you to write a rule the initial term should be in your expression thingy, but for reccurennce relations you're doing it wrong if the initial term is in the expression! (should only by in the V0=x like Lear said)

[studyingg]

Matrices:

Sometimes s0 (the initial state matrix) is defined as being the 'first week'/'first month' -- so if it asks you to find the state matrix for the second week your answer should be s1 and not s2

[Lear]

Sig figs =\= Decimal points.

[studyingg]

Graphs:
-If you have two missing variables, the only ways to find them is through simultaneous equations, if there is not enough information from the question to set up simultaneous equations, then there has to be a relationship between x and y, where y can be expressed in terms of x. (2016 last question)

-make sure to include the domain restrictions when writing a piecewise function

-if it asks you to write an equation write it interms of the actual variables given, not x and y

[AngelWings]

Just going to throw in some older threads here from either recently or past years. Link here.

The biggest issues students have are that people misread the question and in the ones with worded answers, they write things that seem less relevant than the right answer. I'd recommend having a template for worded answers, particularly in the data analysis core module. This stops you from deviating too far from what the examiners expect you to provide. Template can often be found in notes from teachers or typically supplied from Further teachers upon request. Good bit of side advice also: know your bound reference. Not too late to chop a corner and colour code according to module. Takes 5 minutes.

(Bolded applies to practically every subject.) I'll go find this one question that pops up every few years and always, always gets a low percentage who get it right, however, this question is unlikely to pop up this year because IIRC, it happened last year. And then there are the notorious ones that get out into the public media. 50c question anybody?EDIT: Found the question I referred to in the previous paragraph: link here.

[VeryJuicyLemon]

when you realise you don't need to show working out as correct answer equals to full marks. Which can save you time.

You only show working out when vcaa asked you to "show"

[Lear]

What really? That is new to me. I’ve always put working out for those two marker questions such as the last ones on financial maths.

[studyingg]

Yeah, that's true but i'm gonna play it safe and always show some working out.

[Aaron]

when you realise you don't need to show working out as correct answer equals to full marks. Which can save you time.

You only show working out when vcaa asked you to "show"

But at the same time, would you not play it safe just incase you get it wrong and end up with zero? You're guaranteed a zero if you show no working and end up getting the answer wrong, even if it's a minor error. Marks in FM are so important.

Realistically if the question is more than 1 mark, you should be showing working out to be on the safe side. I've always used the rule of thumb as: 1 mark = 1 skill or thing we must demonstrate.. so if something is 5 marks, then 5 things are required... whether that be answers to multi-part questions, steps in working out... etc.

The marks allocated to a particular question give a hint as to how much is required.

[VeryJuicyLemon]

But at the same time, would you not play it safe just incase you get it wrong and end up with zero? You're guaranteed a zero if you show no working and end up getting the answer wrong, even if it's a minor error. Marks in FM are so important.

Realistically if the question is more than 1 mark, you should be showing working out to be on the safe side. I've always used the rule of thumb as: 1 mark = 1 skill or thing we must demonstrate.. so if something is 5 marks, then 5 things are required... whether that be answers to multi-part questions, steps in working out... etc.

The marks allocated to a particular question give a hint as to how much is required.

If only VCAA is generous enough to give us time to play safe. Imo, include working out for questions that you are somewhat unsure of, whilst question that can be simply solved through cas, leave no working. Since you can just redo the question on your cas to double check (much less time consuming)

Cause for each correct answer with working, is time wasted on working. You really want to maximise your time given from VCAA imo

[Lear]

Only a small number of questions in vcaa exam 2 offer more than one mark. For one markers I’d suggest just going with the answer, however for two markers I always leave working out in nice and tidy fashion (for example financial solver inputs for that 2-3 mark question at the end of financial).

Even through doing this and doing questions at a snail pace I think there is sufficient time to finish.

[VeryJuicyLemon]

Only a small number of questions in vcaa exam 2 offer more than one mark. For one markers I’d suggest just going with the answer, however for two markers I always leave working out in nice and tidy fashion (for example financial solver inputs for that 2-3 mark question at the end of financial).

Even through doing this and doing questions at a snail pace I think there is sufficient time to finish.

Whatever works for you

[S_R_K]

Data:

Not reading scales on scatter plots or graphs of least-squares lines.

Not using a ruler to sketch lines.

Not plotting points to sketch lines accurately.

Incorrect order of subtraction when calculating residuals or standardised scores.

Misreading "correlation coefficient" as the coefficient of determination, or vice versa.

Financial:

Not writing answers correct to the nearest cent and including all the necessary digits, even when the answers are something like $200.00 or $200.10.

Not recognising a perpetuity / interest-only loan, and hence not recognising that the balance doesn't change.

Not adjusting the interest rate for the number of compounding periods per year when using a formula.

Financial, when asked to use recurrence relation or write a recurrence relation YOU MUST MUST Write the initial term first.

This is WRONG
Vn+1=0.5Vn where V0 = 1000

This is correct
V0=1000, Vn+1=0.5Vn


Stupid thing that examiners are fussy about that textbooks don’t teach (and often do incorrect themselves)

Where did you hear this? This is beyond insane.