I said mean stays the same and then gave an explanation that this was because the new value was equal to the mean. I said that s.d would stay the same as it is 0 deviations above the mean (I know this part is wrong) How many marks would I get it? The question was out of 3
I think you'll get one mark for that answer.
I'm guessing the mark scheme would be 1 mark for the mean staying the same.
1 mark for the standard deviation changing and 1 mark for the reason which I think is that the standard deviation looks at the spread of data.
On the topic of the mean-If you put the new value, 3.43, into the table and work out a new mean, the longer way, the mean would decrease. However a better way would be to combine means, which would keep it the same.I would imagine Edexcel would allow either as you can reason it either way, but this way makes more sense.
That's for combining the mean though. I thought we were asked what will happen to the mean if one value had been added into the observations, not combining two different means.
I got the numbers for p + q wrong in the sarah and rebecca question, i have no clue how, will I get error carried forward, or method marks for the rest? I know my method are right but obviously the answers will be wrong
I messed up big time. I read the whole 1/X thing as 1 over the probability rather than the x values. Damn I though because it was a capital x it meant probability.
Arsey commented on the other thread saying that he found the paper quite difficult too and he thinks grade boundaries will be lowerr That gave me hope lol
I messed up big time. I read the whole 1/X thing as 1 over the probability rather than the x values. Damn I though because it was a capital x it meant probability.
It was a normal distribution with mean 3.43 and a standard deviation I can't quite remember - sorry! But standardising (3-3.43)/s.d. gave a z value with p(Z<z) of 0.2546
Was the standard deviation not 5? Then how do you do it?
How do you know? Or just hoping because I got the same 0.465 and 0.450
same i got 0.450 for sarah winning and then did 1-(P(sarah won)+P(draw) =P(rebecca won) so i dont know where i couldve gone wrong but noone really seems to have these answers :/