explain questions on Stats 1 AQA Jan

Discussion in 'Mathematics' started by ResourceFinder, Mar 28, 2011.

1. ResourceFinder

We have sent for some papers AQA Jan S1 and are not entirely satisfied with some of the marks for explain questions

If anyone has the paper ... the question that asks
(a) explain why m>1 and why P(number less than x less than number) is approx 1

Answer to the first ... I simply put "because the majority of results are above 1 and those less than 1 are close to 1" and to the second "the vast majority of results are within the range [number, number]

The student answers are different but present some similarities ... no marks given

What should we have said

Oh and the cricket ball explain one ... I put Strong +ve corr between circ and weight within the circ range of [value, value] one student received both marks in spite of not mentioning an acceptable range of values

2. briceanusNew commenter

Part 2 first.
With AQA you don't need to mention that the correlation is only valid between lowest and highest control variables, only its strength, sign, and linearity (if graph available). Of course, if a question asks why an extrapolated value may be uneliable, you need to state why, ut NOT when describing correlation.

Part 1 next
ths is question 3, part d.
m>1 is supported simply by the fact that the 99% confidence interval is (1.051, 1.073), therefore the true mean is highly likely to be above 1.
P(0.94<x<1.16) is approx 1 as 99 out of the 100 sampled values lie within that range , and even that one could measure 1.16 [1.16<x<1.18 has one entrant]

AQA aren't seeking statistically faultless arguments, they are seeking a reasonable understanding of what the calculations indicate.

Hope this helps.
Bric

3. ResourceFinder

Thanks Bric

Fair enough on part 2 ... there was a question later on that referred to a value outside of range

A student gave an answer very similar to your m>1 one and received no marks ... I will look again tomorrow

Again, thanks ... none of us are Statisticians and I did not teach the module ... the teacher who did has struggled with some of the explain responses so I may be back