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# S2 PDF/CDF quartiles Tweet

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1. S2 PDF/CDF quartiles
Q7 (g)

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The mark scheme says since it's a symmetric distribution, to get Q3 you do 5-1.3
Where did the 1.3 come from/what is it?
2. Re: S2 PDF/CDF quartiles
What exam board is this?
3. Re: S2 PDF/CDF quartiles
Using symmetry, the distance from 5 to Q3 is the same as the distance from 1 to Q1, as 1 and 5 are the endpoints. Make sense?
4. Re: S2 PDF/CDF quartiles
(Original post by snow leopard)
...
If the lower quartile is at 2.3, which is 1.3 above the bottom of the distribution, then the upper quartile is 1.3 below the top of the distribution; if you'll pardon the loose terminology.
5. Re: S2 PDF/CDF quartiles
I just did this question a few minutes ago!!
6. Re: S2 PDF/CDF quartiles
(Original post by Jin3011)
What exam board is this?
Edexcel, why?

(Original post by ghostwalker)
If the lower quartile is at 2.3, which is 1.3 above the bottom of the distribution, then the upper quartile is 1.3 below the top of the distribution; if you'll pardon the loose terminology.
Right I see. My mistake was thinking the bottom of the distribution was 0, when it's actually 1. Thanks
7. Re: S2 PDF/CDF quartiles
(Original post by snow leopard)
Edexcel, why?
Was just curious
8. Re: S2 PDF/CDF quartiles
Trying to calculate medians and quartiles. If you have multiple functions in your F(x), how do you know which one to equal to 1/2 to find the median, for example?
9. Re: S2 PDF/CDF quartiles
(Original post by D_Akinola)
Trying to calculate medians and quartiles. If you have multiple functions in your F(x), how do you know which one to equal to 1/2 to find the median, for example?
If you already have F(x), then evaluating that function at the end of the interval corresponding to each part definition will tell which is the appropriate part to use.
10. Re: S2 PDF/CDF quartiles
Thanks.