Taking apart my last mock: where 211 marks actually went

My last mock was 509 out of 720. That's a decent number. It also means I lost 211 marks, and I'd like to show where, because the loss is the only part of the paper I can do anything about.

I'm putting my full analysis here because when I asked people how to analyse a mock they said "look at your weak areas", which, thanks, is exactly what I wanted to figure out. So here's how I do it, with my own numbers from last Saturday. (Class 12, boards in a few months, so this is a quick version.)

Step 1: Subject-wise snapshot

The paper is 180 questions: Physics 45, Chemistry 45, Biology 90. Marking is +4 for correct, -1 for wrong, 0 for unattempted.

Subject	Attempted	Correct	Wrong	Marks
Physics	40	28	12	112 - 12 = 100
Chemistry	43	34	9	136 - 9 = 127
Biology	88	74	14	296 - 14 = 282
Total	171	136	35	544 - 35 = 509

Quick sanity check I always do: marks = 4 × correct - wrong. 4 × 136 = 544, minus 35 = 509. If the sum doesn't match, I mis-copied something.

Biology is at 282 out of 360, so about 78 percent, Chemistry about 71 percent of its 180, and Physics 100 out of 180, so 56 percent. I don't need to tell you where the problem is. Physics is the weak one, as always. But the number "56 percent" is only the headline. It doesn't tell me why.

Step 2: Where the 211 went

Each wrong answer costs me 5 marks relative to getting it right (I lose the +4 I could have had and get -1). Each unattempted question costs 4. So:

• 35 wrong x 5 = 175 marks
• 9 unattempted x 4 = 36 marks
• 175 + 36 = 211 ✓

That's a useful reframe. My 35 wrong answers cost far more than my 9 skipped ones. If I could convert even a third of the wrong ones, I'd gain about 58 marks, which is more than all the skipped questions combined.

Step 3: Sort the 35 wrong answers into types

I go through them one by one with the paper beside me and put each into a category. Mine were:

Type	Count	Marks lost (x5)
Concept gap (didn't know the idea)	9	45
Silly (calculation, misread, sign)	12	60
Guess (no idea, picked one)	8	40
Time pressure (rushed the last 20)	6	30
Total	35	175

Look at what that says. The thing I'd always blamed, "weak concepts", is only 45 marks. The silly ones are more than that, 60 marks. If I had said "I need to study more Physics" I would've gone and done three more hours of Physics theory. What I actually need is a habit: read the question twice, write units, check the sign.

Step 4: Pick the leaks to fix

I do not try to fix everything. I pick the two biggest and write a rule for each.

Silly errors (60 marks). Of the 12, seven were in Physics numericals: three unit slips (cm vs m), two sign errors in potential/energy, two where I used the wrong value. Rule for the next two weeks: after every numerical, spend 10 seconds writing the unit of the answer in my head and the sign check. Not more time on each question, just a fixed 10-second closing ritual.

Guesses (40 marks). Eight guesses, five of them wrong enough to hurt. Here's the thing about guessing in a paper with negative marking. If you have no clue between 4 options, the expected gain from a guess is:

$\tfrac{1}{4}(+4) + \tfrac{3}{4}(-1) = +0.25$

That's basically nothing. But if I can honestly rule out two options, it becomes:

$\tfrac{1}{2}(+4) + \tfrac{1}{2}(-1) = +1.5$

So my rule is: guess only if I can kill at least two options for a reason I can say in one line. Otherwise leave it. I'd rather lose 0 than gamble for 0.25.

Step 5: Concept gaps, tiny list

Nine questions, but when I grouped them there were only three chapters involved: two in Physics (a modern physics one and a rotational motion one), one in Chemistry (a coordination compounds one). So the "study plan" for the week isn't "do Physics". It's three specific chapters.

Step 6: What I'm NOT doing

I'm not comparing this to anyone's score. I'm not predicting a rank from it. One paper has its own difficulty level and its own bad luck. I'm treating the 509 as a reading on a thermometer, not a verdict on my future.

I'm also not retaking the same paper in the next two weeks. That'd just be memory.

What I'd tell you to copy

If you're doing this for the first time, it takes me about 90 minutes to do properly. The order is: count, compute the loss, sort wrong answers by type, pick two leaks, write one rule each, list the specific chapters. Write the rules on a sticky note and put it on the desk next to the pen for the next paper. In the next mock, I check whether the sticky note rules were followed first, before looking at the score. If I followed them, a drop in marks is variance. If I didn't, that's the real problem.

Last thing. 211 marks sounds scary. But 175 of those are wrong answers on questions I attempted, which means I was close. Every one of those was a question where I sat and thought I knew something. That's much easier to fix than not knowing the syllabus. That's why I'm weirdly cheerful about this mock.