GCSE revision Maths

Triggaaar · Jun 7, 2017

All times are 26 seconds and a fraction of a second.

The decimal fractions for Lizzie are 0.3, 0.2, 0.7, 0.3, and 0.5.
That gives a total of 2 seconds. 2 seconds divided by 5 is 0.4 seconds. So her average time is 26.4 seconds.

The decimal fractions for Megan are 0.5, 0.7, 0.1, 0.3, 0.9, and 0.5.
That gives a total of 3 seconds. 3 seconds divided by 6 is 0.5 seconds. So her average time is 26.5 seconds.

On average, Lizzie is faster.

Paul Reids Sock · Jun 7, 2017

timbha said:
What's the most appropriate measure ?
Mean, median, standard deviation, average, fastest, slowest - each one could be relevant

Exactly. Is this a case of - say whatever one you want as long as you can back it up.

I suppose one thing that is worth asking - how many marks is this question worth in relation to the others? if it is a lot more then they may be after a number of factors being determined before coming to a conclusion

Triggaaar · Jun 7, 2017

timbha said:
What's the most appropriate measure ?
Mean, median, standard deviation, average, fastest, slowest - each one could be relevant

Very true, but probably not what GCSE requires

Megan is, after all, the faster swimmer.

warlingham seagull · Jun 7, 2017

Three times are the same for both - 26.7, 26.3, 26.5
Take those out and you are left with:
Lizzie 26.2 & 26.3
Megan 26.1, 26.5, 26.9
Clearly without a calculation - Lizzie's times are faster

Guinness Boy · Jun 7, 2017

In the real world there's so little between them that I'd make them have a race with winner takes all to see how they coped with the pressure. Then I'd go down the pub

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Justice · Jun 7, 2017

Bruntburger said:
Before you ask I don't know how good each swimmer looks in a bikini?

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If someone on here asked what school girls looked like in a bikini I would be more that concerned tbh.

AZ Gull · Jun 7, 2017

Triggaaar said:
Megan is, after all, the faster swimmer.

And the slower swimmer.

studio150 · Jun 7, 2017

Neither as due to the Tory Educational budget cuts, the school have had to cut back on out of school activities and are no longer entering any school teams. Further they have drained the pool as it is too costly to run and have instead moved desk and chairs into the dry pool so that it can be used for the forthcoming GSCE maths exam.

NB The correct answer has been provided by many already

KingKev · Jun 7, 2017

It's asking for a discursive answer that demonstrates understanding. So you can look at the actual mean, then fastest and slowest times then mention standard deviation from the mean (difficult to work out manually but possible) and then go for a proxy of std deviation by taking out fastest and slowest times and averaging the remainder
You still end up going for the first swimmer I think - unless you want to argue that the fastest time rules. Don't think the choice of swimmer matters, just the showing that you understand the ways you can analyse this data...

Triggaaar · Jun 7, 2017

AZ Gull said:
And the slower swimmer.

That's like saying that out of me and Usain Bolt, he is the slower runner, as he's probably run a slower 100m than I have (which he is likely to have done when injured in training).

Who is fastest is simply about your fastest time, not whether or not you've sometimes had a slow time.

The Antikythera Mechanism · Jun 7, 2017

Bloody hell, is this what GCSE's have come to? This is 11 plus stuff.

Harry Wilson's tackle · Jun 7, 2017

KingKev said:
It's asking for a discursive answer that demonstrates understanding. So you can look at the actual mean, then fastest and slowest times then mention standard deviation from the mean (difficult to work out manually but possible) and then go for a proxy of std deviation by taking out fastest and slowest times and averaging the remainder
You still end up going for the first swimmer I think - unless you want to argue that the fastest time rules. Don't think the choice of swimmer matters, just the showing that you understand the ways you can analyse this data...

The problem is that in this idiotic world, there will be one 'officially correct' answer and everyone who who gives a different (measured) answer will get zero. I am not sure what happens with GCSEs but at many universities, any question that is answered 'wrongly' by a disproportionate percentage of students ('disproportionate' can be defined in different ways) can be excluded from the assessment. But this rule is not applied equally be every institution. Coincidentally I have spent all day doing my external examiner visit at a London medical school :wozza:

Is it PotG? · Jun 7, 2017

They should both be selected if their attitude is right, it is not about winning,

Stato · Jun 7, 2017

I'd say that the selection of Lizzie because of her fastest mean average time would get some marks. It looks like further marks may be available by showing working to prove that she also has the fastest median time and the fastest mode. I guess this because they have included repeated times in both girls ranges to ensure that a mode can be shown.

Good luck to your daughter. Mine's going through the same.

Merdalfthewizard · Jun 7, 2017

Mrs Merdalf is a swimming coach and I showed her this, the first thing she asked was how long is the pool 25m or 50m. Never ask a professional, they always deviate

Stato · Jun 7, 2017

My daughter tells me that they teach range now as well as mean, median and mode. Deduct the lowest time from the highest time to get each swimmer's range. Lizzie has the lowest average using mean, median, mode and range. She's grateful for the tip about adding just the decimals. She would have struggled through adding all the 26s too.

Papak · Jun 7, 2017

Springal said:
And regardless of the outcome of this exam, your daughter will be in a job where she can use a spreadsheet to work this stuff out rendering this Maths exam completely pointless.

I'm not sure Diane Abbot would agree.

timbha · Jun 7, 2017

Stato said:
My daughter tells me that they teach range now as well as mean, median and mode. Deduct the lowest time from the highest time to get each swimmer's range. Lizzie has the lowest average using mean, median, mode and range. She's grateful for the tip about adding just the decimals. She would have struggled through adding all the 26s too.

even if two of the times had been say 25.6 and 27.1 you could still use the "26" factor, ie the first one would be -0.4 and the 2nd +1.1 when working out the average to add to the 26 at the end

AZ Gull · Jun 7, 2017

Triggaaar said:
That's like saying that out of me and Usain Bolt, he is the slower runner, as he's probably run a slower 100m than I have (which he is likely to have done when injured in training).

I remain unconvinced that Bolt has run a slower 100m than you.

Triggaaar said:
Who is fastest is simply about your fastest time, not whether or not you've sometimes had a slow time.

Indeed. Megan has proven in her trials that she can swim faster than Lizzie. She has also proven that she is more inconsistent than Lizzie. On her day she would beat Lizzie, but when it isn't her day she would lose to Lizzie.

Cheshire Cat · Jun 7, 2017

The real question should be, who was taking the performance enhancing drugs, in which race, and did they have an effect?

Answer - Megan in the third race, but only in that race. After a while they wore off, and her supplier had gone home.

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GCSE revision Maths

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