lightningdoritos
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So this is the weird paper Edexcel S1 May 2013 (R) and it's question 3(e) that I don't understand....I guessed that it was 12 tomato plants but I don't understand how you work it out...please help!
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Puddles the Monkey
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(Original post by lightningdoritos)
So this is the weird paper Edexcel S1 May 2013 (R) and it's question 3(e) that I don't understand....I guessed that it was 12 tomato plants but I don't understand how you work it out...please help!
Heya, I'm going to put this in the Maths forum for you as you should get more responses there.

You should also check out the forum to see if there's any other threads there which might be helpful to you! http://www.thestudentroom.co.uk/forumdisplay.php?f=38
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davros
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(Original post by lightningdoritos)
So this is the weird paper Edexcel S1 May 2013 (R) and it's question 3(e) that I don't understand....I guessed that it was 12 tomato plants but I don't understand how you work it out...please help!
You really need to post the actual question, otherwise most people aren't going to have a clue what this is about!
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lightningdoritos
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(Original post by davros)
You really need to post the actual question, otherwise most people aren't going to have a clue what this is about!
Ah okay sorry will do
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studentwiz
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(Original post by lightningdoritos)
Ah okay sorry will do
I don't get it did you manage to get an answer?
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lightningdoritos
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(Original post by studentwiz)
I don't get it did you manage to get an answer?
At first I just guessed and got the right answer but then I used a histogram although that's not how you're 'supposed' to do it apparently? So basically I drew the histogram for the last three groups and worked out frequency density for each. Then I "cut" the 15-25 bar down into two parts (due to the mean+1 standard deviation equalling 18.3 or something). Then I worked out the area of the 18.3-25 'half' bar which was the frequency and added it on to the four in the last group.

Hope that made sense!
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studentwiz
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(Original post by lightningdoritos)
At first I just guessed and got the right answer but then I used a histogram although that's not how you're 'supposed' to do it apparently? So basically I drew the histogram for the last three groups and worked out frequency density for each. Then I "cut" the 15-25 bar down into two parts (due to the mean+1 standard deviation equalling 18.3 or something). Then I worked out the area of the 18.3-25 'half' bar which was the frequency and added it on to the four in the last group.

Hope that made sense!
that's mad confusing, its fine tho. Have you done question 5d and e if so could explain that I feel those are some easy marks.

and question 7g I don't get that one
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lightningdoritos
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(Original post by studentwiz)
that's mad confusing, its fine tho. Have you done question 5d and e if so could explain that I feel those are some easy marks.

and question 7g I don't get that one
Yeah I know.....only two marks as well!

Sorry but I haven't done those ones...I'm doing a Maths Tallis paper so it's not really a full paper, just random questions...but I'll try and find out when I do it!
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Gome44
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Add the mean to the standard deviation. You should get 18.2444..... Now anything above this value is what you want, so you can use interpolation reversed to estimate what frequency this occurs at. Then do 70-that frequency, and you should get the required answer
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studentwiz
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(Original post by Gome44)
Add the mean to the standard deviation. You should get 18.2444..... Now anything above this value is what you want, so you can use interpolation reversed to estimate what frequency this occurs at. Then do 70-that frequency, and you should get the required answer
use interpolation on what? the mean??
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Gome44
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(Original post by studentwiz)
use interpolation on what? the mean??
Interpolation is estimating the value of something in grouped data if you know the frequency. This time, you know the value in the grouped data (18.244....), which is the mean + 1sd, so you can work backwards to find out what frequency this occurs at
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studentwiz
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(Original post by Gome44)
Interpolation is estimating the value of something in grouped data if you know the frequency. This time, you know the value in the grouped data (18.244....), which is the mean + 1sd, so you can work backwards to find out what frequency this occurs at
yes but how do you use interpolation in this case?
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Super199
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I hate bloody questions like these
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(Original post by studentwiz)
yes but how do you use interpolation in this case?
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I followed all the way till tposition -54 why minus 54?
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Gome44
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That's the cumulative frequency upto the class 15<y<25

I have written the formula for interpolation on the sheet. The formula is just a general rearrangement of the ratio method in the textbook
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