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Reply 80
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!
Reply 81
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

Is that the correct answer?


No :/ but that's the same answer I got! The answer is 0.193 :frown:
Reply 82
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!!
Reply 83
Original post by zangorou
No :/ but that's the same answer I got! The answer is 0.193 :frown:


Are you sure? We can't both have done it wrong surely...
:colondollar:
Reply 84
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!
Reply 85
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
Reply 86
Original post by jo7777
Are you sure? We can't both have done it wrong surely...
:colondollar:


Yeah :frown:

mathsq.png
Reply 87
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?
Reply 88
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?"
Reply 89
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!
Reply 90
Original post by jo7777
Nope I couldn't find it!


I'll sort that out for you! Check your inbox.
Reply 91
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 :smile:
Reply 92
Original post by TypoCool
I'll sort that out for you! Check your inbox.


LEGEND
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.
Reply 94
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 :smile:
Don't forget about how the skewness affects it too.
I really hate Probability questions in general
Reply 96
Probability is the absolute worst. It just doesn't make sense!
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
Reply 98
I hear ya sista hehe
Reply 99
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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