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S2 frequency, discrete and continuous probability distributions

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Hi guys 😄

Is somebody able to explain these two images to me please?

Thank you so much ☺️
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Original post by jasminetwine
image.jpeg
Attachment not found


Hi guys 😄

Is somebody able to explain these two images to me please?

Thank you so much ☺️


How much of it do you understand already? :h:
Original post by SeanFM
How much of it do you understand already? :h:


I don't understand any of the first photo with the graph (frequency -> discrete or discrete -> frequency)
In the second photo, what do we need to know for the Edexcel S2 exam? I think I understand the 2nd and 3rd column, but not the first! 🙈
Thanks!
Original post by jasminetwine
I don't understand any of the first photo with the graph (frequency -> discrete or discrete -> frequency)
In the second photo, what do we need to know for the Edexcel S2 exam? I think I understand the 2nd and 3rd column, but not the first! 🙈
Thanks!


To be honest - those photos aren't by any means a good way of learning S2 - the textbook is much better.

Those symbols will all seem pretty much meaningless if they're not taught in the right way.

Starting with the second photo:

The frequency distribution - just think of it being like a tally chart. x1, x2 etc being the different measurements (eg age, shoe size, IQ etc) and f1, f2 etc being their corresponding frequencies (how many there are).

If you sum all the frequencies, that's the number of (people or other objects) that you've measured.

The next one works out the mean, m. Just like if you had 3 people aged 1, 5 people aged 2 and 7 people aged 3 then the average is 3 * 1 + 5*2 + 7* 3 / (3 + 5 + 7) = 34/15 (= 2.26, which makes sense as the average age leans towards 3, which has more people than 1)

Then the s^2 is for working out sample variance.

You need to know the last two columns but the first one.. probably not.

The first photo, the first formula is just saying that the probability of something occuring is just like a fraction (how many times it occurs / total number of things) for example, if you had 3 red balls and 2 blue ones in a box then you would say probability of getting a red is 3/5 and probability of blue is 2/5. 3 is the frequency of red, 5 is the total so 3/5 is the probability of red.

The second bit is saying that (with the area of that graph being 1, the probability of some event x happening is the area of that region of the graph. It's being too ambiguous for my liking though.

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