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OCR MEI - S1 - 20th May 2015

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Reply 60
Avatar for alipx
alipx
4
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 :smile:
Reply 61
Avatar for alipx
alipx
4
Original post by the bear
yes, exactly.


Any chance you could explain central tendency to me please? :smile:
Reply 62
Avatar for zirak46
zirak46
8
Original post by alipx
Any chance you could explain central tendency to me please? :smile:


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)
(edited 8 years ago)
Reply 63
Avatar for alipx
alipx
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
Reply 64
Avatar for zirak46
zirak46
8
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.
Reply 65
Avatar for alipx
alipx
4
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 :tongue:
Reply 66
Avatar for zirak46
zirak46
8
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 :tongue:


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
Reply 67
Avatar for alipx
alipx
4
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!!
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:

Please save me!
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
Reply 70
Avatar for zirak46
zirak46
8
Original post by AmateurMathsGeek
Range is largest - smallest
Midrange is (largest+smallest) divide by 2


Oh snap yeah cheers haha!
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?
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 ?
What an exam!! So easy considering the amount of revision I did
I was rushed for time a bit. What did you get for the last 2?
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.
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
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?
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?
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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