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# how to calculate mean from grouped data on graphical calculator? Watch

1. does anyone know how to work out estimates of the mean and standard deviation from data that has midpoints, but more specifically on a graphical calculator? i have a standard casio fx-9750GII. i did this so long ago that i can't remember what to do. i've plugged in the midpoints into one column and the frequency into another, but when i calculate the mean from that its wrong! any help appreciated!
2. (Original post by georgiaaaxo)
does anyone know how to work out estimates of the mean and standard deviation from data that has midpoints, but more specifically on a graphical calculator? i have a standard casio fx-9750GII. i did this so long ago that i can't remember what to do. i've plugged in the midpoints into one column and the frequency into another, but when i calculate the mean from that its wrong! any help appreciated!
your method sounds correct... maybe you worked out the midpoints incorrectly ?
3. (Original post by the bear)
your method sounds correct... maybe you worked out the midpoints incorrectly ?
weird..i'm close to the answer but not close enough if i attach the question would you be able to tell me if i'm doing it right?

http://filestore.aqa.org.uk/subjects...W-QP-JAN11.PDF

its question 3, and i'm on part b. i got the midpoints as 0.96,0.99,1.02,1.05 etc etc basically adding 0.03 each time!
4. (Original post by georgiaaaxo)
weird..i'm close to the answer but not close enough if i attach the question would you be able to tell me if i'm doing it right?

http://filestore.aqa.org.uk/subjects...W-QP-JAN11.PDF

its question 3, and i'm on part b. i got the midpoints as 0.96,0.99,1.02,1.05 etc etc basically adding 0.03 each time!
your midpoints look fine... have you checked that you entered the frequencies exactly ?
5. (Original post by the bear)
your midpoints look fine... have you checked that you entered the frequencies exactly ?
okay, and yeah i've checked. i get 1.065 as the mean but it says its 1.062 :P
6. (Original post by georgiaaaxo)
okay, and yeah i've checked. i get 1.065 as the mean but it says its 1.062 :P
it's definitely 1.062... the total of x*f is 106.2 not 106.5
7. (Original post by the bear)
it's definitely 1.062... the total of x*f is 106.2 not 106.5
ah i dont know what i'm doing wrong then! ah don't worry i'll have another look at it but i can't see where i'm going wrong thanks though!
8. all i can think is that you may have typed 18 instead of 15,

9. If ur GDC is like my Ti-84 Plus. When I get the mean for a group of data, I have to put L1 (The column which contains the midpoints) into List and L2 (The frequencies) into Freqlist and then calculate.

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Updated: April 13, 2013
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