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    Chapter 4 representation of data ( was easy until this question, or I might just be missing something completely..).
    It’s the mixed exercise 4G question 5 , a histogram question. Please if you have the book can you explain to me how to answer this question as I thought it was meant to be simple but when I went on solution bank they started throwing in random algebra thanks
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    (Original post by Juleh)
    Chapter 4 representation of data ( was easy until this question, or I might just be missing something completely..).
    It’s the mixed exercise 4G question 5 , a histogram question. Please if you have the book can you explain to me how to answer this question as I thought it was meant to be simple but when I went on solution bank they started throwing in random algebra thanks
    It''s saying that k*the area = frequency, for the life of me I can't find any information on this but it rings a bell.

    I think just remember this and... it may not come up.
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    (Original post by Kevin De Bruyne)
    It''s saying that k*the area = frequency, for the life of me I can't find any information on this but it rings a bell.

    I think just remember this and... it may not come up.
    I don’t understand where k comes from? Have you looked at the question, it seems clear to me that you just multiply class width by the fd to calculate frequency. So confusing, and I have no one to really help as I’m retaking this exam in my gap year
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    (Original post by Juleh)
    I don’t understand where k comes from? Have you looked at the question, it seems clear to me that you just multiply class width by the fd to calculate frequency. So confusing, and I have no one to really help as I’m retaking this exam in my gap year
    The area is proportional to the frequency, I.e. Frequency = k* area. I don't know why, I guess it's more useful when you're representing large numbers with the area.

    When k = 1, frequency = area = class width * fd but this is not guaranteed. From the other questions in this chapter it seems your trigger should be when it tells you the frequency for one class, find its area. Is it equal to the frequency? If yes, then k = 1 and you have no problems interpreting fd * cw. If it's not, as in this example where in= 2, then the frequency is twice the area of each bar... so you do 2*fd*cw

    If that isn't clear, let's take a simplified example. You have identical lego blocks which are of equal value but the value is unknown. If there is a tower with 5 blocks and I tell you it's value is £200 and ask you to find the value of a tower 8 blocks high, then you would work out that 1 block is £40 and so 8 blocks are £320.

    How does this apply to frequency density? Well... you don't know what the value of area (class width * frequency density) is compared to the actual frequency. They could be equal, but they might not be. The same way you initially don't know the value of the lego blocks until I tell you the cost of one with a certain number of blocks.

    So it seems the formula is k \times frequency density = \frac{ frequency}{class width} where k is some number that we initially do not know. When it is 1, frequency density = \frac{frequency}{class width} .

    The natural question is then: 'how do I know what k is?' To which the answer is, the same way where information is given in the lego example and in this question.

    The natural question that comes after is: 'so what do I do in the exam?'

    If you are asked to calculate frequency density for whatever reason, then assume k=1 unless you are lead to believe otherwise

    if you are given a graph and some initial information such as 'the group between age 10 and 12 had 20 cakes', then work out the area for that group. Let's say the frequency density was 5, then the area would be 5*2. So area = 10 but frequency is 20 so this tells us that you need to multiply area by 2 to get the frequency. You then apply this for whatever question you are actually supposed to answer, just before you do this you need to know what k is in the formula area * k = frequency where area is frequency density * class width
 
 
 
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