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# Ocr mei statistics 1 exam thread (24/05/13) watch

1. Just to clear up I know a few people are confused about medians in Histograms and cumulative frequency graphs.

It's:
Histograms - n+1/2

cumulative frequency - n/2

The before mentioned histogram question where the mark scheme says it's n/2 is in June 09 paper (question 5 I think) for those wondering!
2. (Original post by jo7777)
So for i)
mean is 83.95/8 = 10.49
sum of squares:
all of the x values squared is 881.2119
881.2119 - 8 x 10.49^2 = 0.8911
0.8911/7 = 0.1273
square root of this is 0.357
so standard deviation is 0.357

No :/ but that's the same answer I got! The answer is 0.193
3. (Original post by TypoCool)
Lol, I'd say that it won't be too difficult! Not much more they can ask, take a look at the 2011 june series which is one of the harder ones, if you master that you' ll get an A for sure!
I didn't quite master it, but I got an A so hoping for the best!!
4. (Original post by zangorou)
No :/ but that's the same answer I got! The answer is 0.193
Are you sure? We can't both have done it wrong surely...
5. (Original post by jo7777)
I didn't quite master it, but I got an A so hoping for the best!!
That's good because that was one of the harder ones. I'm sure tomorrow will be a breeze!
6. (Original post by TypoCool)
That's good because that was one of the harder ones. I'm sure tomorrow will be a breeze!
Are there any other ones which are much harder than the others? Just going through them all
7. (Original post by jo7777)
Are you sure? We can't both have done it wrong surely...
Yeah

8. (Original post by jo7777)
Are there any other ones which are much harder than the others? Just going through them all
I'd say just have a crack at any you haven't done! Their roughly similar have you done jan 13?
9. Could someone tell me the reasons as to why
median
mean
midrange
etc
are better in certain situations?
EG the questions where it asks you: "which would you recommend to measure the central tendency of the data?"
10. (Original post by TypoCool)
I'd say just have a crack at any you haven't done! Their roughly similar have you done jan 13?
Nope I couldn't find it!
11. (Original post by jo7777)
Nope I couldn't find it!
I'll sort that out for you! Check your inbox.
12. (Original post by krishkmistry)
Absolute weird question this - but because I remember the sigma as e - if I write e instead of the sigma sign,will I get penalised ?

Posted from TSR Mobile
no you wont as long as you write it as the sidewards M or just write the sum of its what it means
13. (Original post by TypoCool)
I'll sort that out for you! Check your inbox.
LEGEND
14. (Original post by jo7777)
Could someone tell me the reasons as to why
median
mean
midrange
etc
are better in certain situations?
EG the questions where it asks you: "which would you recommend to measure the central tendency of the data?"
Median, this is a good when there is outliers, as outliers have NO effect on the median, as it's the middle value, so a really high/low value will not affect this average, so recommend the median when outliers are involved.

The Mean is also good if the data is condensed, however it IS affected by outliers also, although outliers do not affect it as much as the Mid Range. This is usually the best with lots of data with no outliers. I'd recommend the mean when outliers are not involved.

Mid Range is only good if the data is condensed, as it involves the highest value & lowest value, so it's bad if there is a high range, as outliers affect the mid range badly.
Recommened this or the mean when NO outliers are involved.
15. (Original post by DarkWillow)

Mid Range is only good if the data is condensed, as it involves the highest value & lowest value, so it's bad if there is a high range, as outliers affect the mid range badly.
Recommened this or the mean when NO outliers are involved.
Thank you! Exactly what I needed
Don't forget about how the skewness affects it too.
16. I really hate Probability questions in general
17. Probability is the absolute worst. It just doesn't make sense!
18. Lol, I know the formulas for it & can do it, but I'm always paranoid & seem to make lots of mistakes in that section! I don't like Probability & the Null Hypothesis stuff
19. I hear ya sista hehe
20. (Original post by DarkWillow)
Median, this is a good when there is outliers, as outliers have NO effect on the median, as it's the middle value, so a really high/low value will not affect this average, so recommend the median when outliers are involved.

The Mean is also good if the data is condensed, however it IS affected by outliers also, although outliers do not affect it as much as the Mid Range. This is usually the best with lots of data with no outliers. I'd recommend the mean when outliers are not involved.

Mid Range is only good if the data is condensed, as it involves the highest value & lowest value, so it's bad if there is a high range, as outliers affect the mid range badly.
Recommened this or the mean when NO outliers are involved.

What about the interquartile range, variance and standard deviation? What does the skewness affect?

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