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# OCR MEI - S1 - 20th May 2015 watch

1. (Original post by tambeshakunt)
Do you ever do strict inequalities for hypothesis when carrying out the test? Or is it always greater than or equal to or less than or equal to?
Pretty sure it's alway greater than or equal / less than or equal, thats what they use in the formula book above the hypothesis testing tables
2. (Original post by the bear)
yes, exactly.
Any chance you could explain central tendency to me please?
3. (Original post by alipx)
Any chance you could explain central tendency to me please?
Central tendency is basically how close a value is to the middle - where middle of data is.
Measured by the 'M's: median, mode, mean & midrange (largest - smallest over 2)
4. (Original post by zirak46)
Central tendency is basically how close a value is to the middle.
Measured by the 'M's: median, mode, mean & midrange (largest - smallest over 2)
Thanks, So if the data was really spread out which would be the best measure of central tendency? I'm thinking the median? but I'm not sure
5. (Original post by alipx)
Thanks, So if the data was really spread out which would be the best measure of central tendency? I'm thinking the median? but I'm not sure
How much data is spread is called Variation or Dispersion

That can be measured via range, percintles, quartiles and therefore interquartile range.
6. (Original post by zirak46)
How much data is spread is called Variation or Dispersion

That can be measured via range, percintles, quartiles and therefore interquartile range.
Yeah, but I though sometimes they ask whether the mean or median is more representitive (or something) of the central tendency, how do I know which?

Thanks for your help sorry I know I'm being a bit stupid but I can't quite get my head around it
7. (Original post by alipx)
Yeah, but I though sometimes they ask whether the mean or median is more representitive (or something) of the central tendency, how do I know which?

Thanks for your help sorry I know I'm being a bit stupid but I can't quite get my head around it
Oh I get you - this question has came up on a past paper hasn't it.
Its nothing to do with spread (thats variation)
Central tendancy is basically how where middle of data is, either median, midrange, mode or mean can be better.
Comparing median and mean, median is better.
Median isn't affected by outliers while mean is affected by outliers and if skewness changes. Hope that made sense
8. (Original post by zirak46)
Oh I get you - this question has came up on a past paper hasn't it.
Its nothing to do with spread (thats variation)
Central tendancy is basically how where middle of data is, either median, midrange, mode or mean can be better.
Comparing median and mean, median is better.
Median isn't affected by outliers while mean is affected by outliers and if skewness changes. Hope that made sense
Oh ok yeah that makes so much sense thank you!!
9. Can somebody please give me some top tips for remember equations for standard deviation?
And also the equations regarding independent and conditional events? They're so difficult to get my head around D:

10. (Original post by zirak46)
Central tendency is basically how close a value is to the middle - where middle of data is.
Measured by the 'M's: median, mode, mean & midrange (largest - smallest over 2)
Range is largest - smallest
Midrange is (largest+smallest) divide by 2
11. (Original post by AmateurMathsGeek)
Range is largest - smallest
Midrange is (largest+smallest) divide by 2
Oh snap yeah cheers haha!
12. how did everyone found it? :s
What did you get for the last question? how did you do the cherry one, and all three orange?
13. Did anyone get probability of b given that a as 1? I thought surely if they're all orange then they'll be 100% all the same ?
14. What an exam!! So easy considering the amount of revision I did
15. I was rushed for time a bit. What did you get for the last 2?
16. (Original post by AlexParmenter)
Did anyone get probability of b given that a as 1? I thought surely if they're all orange then they'll be 100% all the same ?
yep i got sth bigger than one, then i told them that is impossible, because biggest prob is one.
17. (Original post by Bellbird)
how did everyone found it? :s
What did you get for the last question? how did you do the cherry one, and all three orange?
I did 6/20 * 5/19 * 15/18

Or whatever the numbers for cherry was but I think thats how you do it
18. (Original post by Bellbird)
yep i got sth bigger than one, then i told them that is impossible, because biggest prob is one.
That's what I wrote - i thought it might be a trick question?
19. (Original post by alicec11)
I did 6/20 * 5/19 * 15/18

Or whatever the numbers for cherry was but I think thats how you do it
I did that. You don't get marked down if you leave your answer as a fraction do you?
20. (Original post by JamesExtra)
I did that. You don't get marked down if you leave your answer as a fraction do you?
I did that too. You can leave it as a fraction or decimal can't you?

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