OCR MEI Decision 2 (D2) 4772: 8 June 2016

Hey, yeah I thought it was really difficult - I couldn't finish it in time. Also, I couldn't seem to do one of the logic proof questions, the circuit one where you had 2 prove (A^B) -> C. I may have missread it in the exam but if it is that then im sure they made a mistake - you can definitely show that (A^B) <- C though, what did you get for this?

For that one I just drew a truth table and took 0 as switch up and 1 as switch down. I'm not sure whether they wanted a worded explanation but some others who took the exam seem to have worded theirs.

Was this for the circuit one?

bad

Were you able to do all of the logic questions?

I'm so pissed; I think I screwed up

I was alright till the switch circuits just wrote a load of bs and hoped for some pity marks. Messed up he simplex the first time and did three iterations before noticing so that was most the time gone

What did you get for the answers, for the logic (not the switching) i got the like "not headlights" and "not dimmed lights" or something. And for the networks i got one of the paths to be like 109 in length? For EMV stuff i got that taking the questionnaire had value of like 5. something. What about u?

What did you get for the answers, for the logic (not the switching) i got the like "not headlights" and "not dimmed lights" or something. And for the networks i got one of the paths to be like 109 in length? For EMV stuff i got that taking the questionnaire had value of like 5. something. What about u?

The headlights were off so the dashboard lights where not dimmed, networks is a blur tbh, was kinda stressed at that point, I remember I changed nothing on the 5th iteration of floyds..? I feel like I got like 4.9991 or something, but really not sure now

The ones I can remember:

Decision Analysis
- Initially, EMV minimised with not getting vaccinated (18?).
- Value of questionnaire was £5.69 (18-12.31).
- To minimise unpleasantness, get vaccinated (EMV depends on how you modelled unpleasantness).

Logic
- We couldn't tell whether she'd go outside. Even if it was warm, we don't know how dry it was. Even then, she might just not feel like going.
- We can deduce that headlights are off and dashboard lights are not dimmed.
- Prove using truth table/Boolean algebra.
- Show how the switching circuit represented (AnB) => C.
- We can deduce that both the ganged switches and D must be up.

LP
- y-x=0 ensured that there would be at least as much expensive paint as there was less expensive paint.
- x+y>= 350 not included since the maximisation will make it as high as it possibly can anyway.
- LP solved to get x = y = 500/3, therefore total area painted = 1000/3 = 333.3.
- When increased budget to £450, there would be x = y = 187.5 therefore total area of 375.
- Not optimal since more area than needed, and he would rather use more expensive paint where possible.
- For two stage, change objective to maximise P = x, introduce x+y=350 using a <= and >= constraint combined. Using artificial and surplus variable. Minimise A to zero and then proceed to maximise P as usual.

Networks
- Route inspection = 109?
- Floyd's - do 4th iteration and show no change on 5th.
- Nearest neighbour and minimum connector - 49(?) and 53(?) upper and lower bounds?
- Interpretation of Hamilton cycle in original network required going via one more node than in complete network.

The ones I can remember:

Decision Analysis
- Initially, EMV minimised with not getting vaccinated (18?).
- Value of questionnaire was £5.69 (18-12.31).
- To minimise unpleasantness, get vaccinated (EMV depends on how you modelled unpleasantness).

Logic
- We couldn't tell whether she'd go outside. Even if it was warm, we don't know how dry it was. Even then, she might just not feel like going.
- We can deduce that headlights are off and dashboard lights are not dimmed.
- Prove using truth table/Boolean algebra.
- Show how the switching circuit represented (AnB) => C.
- We can deduce that both the ganged switches and D must be up.

LP
- y-x=0 ensured that there would be at least as much expensive paint as there was less expensive paint.
- x+y>= 350 not included since the maximisation will make it as high as it possibly can anyway.
- LP solved to get x = y = 500/3, therefore total area painted = 1000/3 = 333.3.
- When increased budget to £450, there would be x = y = 187.5 therefore total area of 375.
- Not optimal since more area than needed, and he would rather use more expensive paint where possible.
- For two stage, change objective to maximise P = x, introduce x+y=350 using a <= and >= constraint combined. Using artificial and surplus variable. Minimise A to zero and then proceed to maximise P as usual.

Networks
- Route inspection = 109?
- Floyd's - do 4th iteration and show no change on 5th.
- Nearest neighbour and minimum connector - 49(?) and 53(?) upper and lower bounds?
- Interpretation of Hamilton cycle in original network required going via one more node than in complete network.

Nice, I got the same answers as you apart from the stupid mistakes i made. However in the exam I had no idea how you could prove

- Show how the switching circuit represented (AnB) => C.

Even now I don't see how you can do it, I must have severely misunderstood the question or they maybe they screwed up?

Apart from that its all good, if you got all those answers you should defo be in for a great mark.

Although I seemed to get right numerical answers, I think my logic proof has let me down. Also I somehow had a negative in my objective function for simplex even though I had finished and got these answers - probably a small sign error.

I'm thinking about 60. I'm slightly worried that the grade boundaries will be high though, because although it seemed tricky in parts, there was not much out of the ordinary.

I actually think they may have messed up the logic question, I seriously don't see how (AnB) => C

If anyone reading this thread did seem to get the proof, could you please explain how to do it / what the question even was?

Have you drawn the truth table out? Because we don't have the diagram it's difficult to replicate accurately.