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The sheer dedication that must've gone into covering the ENTIRE A-Level Maths/Further Maths syllabus is incomprehensible to us mere mortals. You, sir, are a legend.
I wish you were my teacher. I don't know what my teacher was teaching, and why he was teaching these FANCY TERMS; well, now I understand. All credit goes to you sir, my humble wishes for this fruitful channel of yours!
Thanks so much. I was wondering why I was getting a different standard deviation in all my OCR MEI B questions. Now I know they are referring to the sample standard deviation!
I know variance is important in statistics, but I currently only understand it as an intermediate step on the way to calculating the standard deviation. Are there occasions where variance is preferable? Thank you so much for this video :)
That is another calculation: the mean average deviation. It gives a distinctly different and smaller value than the standard deviation. There appears to be a bit of an argument about retiring the standard deviation in favour of it! web.archive.org/web/20140116031136/www.edge.org/response-detail/25401
The standard deviation tells you the average distance each point is away from the mean. So the larger the standard deviation, the more spread out the data is.
Thanks :) Quick question - theres an Edexcel past paper question which refers to Sxy. It looks like it is in reference to correlation between two data sets. Basically it asks to find the PMCC between two datasets and provides Sxx, Syy and Sxy. This is not in my textbook :/
In the exam, could you just use your calculator to obtain standard deviation/variance from the data given in the question? What if you don't show your working?
Can you, or someone explain why the square root makes sense. Because when you have the addition of two numbers squared, the square root does not reverse the squares of the numbers being added together. Furthermore, why does sqrooting the whole fraction makes sense?
Essentially it's a comparison of magnitude. It's kind of like when you use Pythagoras' Theorem. Squaring the sides puts squares on each of the sides of your triangle, so that you're comparing areas. a^2 + b^2 = c^2. Then to find c we square root both sides, c = sqrt(a^2 + b^2) which brings them back down to lengths.
No. To calculate the standard deviation for a set of numbers, you divide by n. Dividing by (n-1) gets you the sample standard deviation, which is used to estimate the population standard deviation. If you are studying OCR MEI, dividing by n is referred to as the root mean square deviation (rmsd).
Dividing by n-1 is the sample standard deviation and variance. If you’re doing OCR MEI then you will refer to dividing by n-1 as the standard deviation and variance, whereas dividing by n is referred to as the root mean square deviation (rmsd) and the mean square deviation (msd)
That's the sample standard deviation s_x which I introduce here: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ts9SWUiFn6k.html. OCR MEI on the other hand considers dividing by n to be the root mean square deviation, and dividing by n-1 to be the standard deviation. So different boards expect slightly different things. It is definitely worth checking your exam board's specification for more information.
![A-Level Maths: L3-11 [Data: Introducing the Variance and Standard Deviation]](/img/logo.svg){kind=logo}
