Maths IA Chi Squared help

Original post by rosiemoonlight

I am currently doing the IB and working on my maths internal assessment. I have conducted a Chi squared independence test but my hand calculated chi squared calc value is different to the one on my GDC. Dose anyone know why this could possibly be?

Post your working here - it's either a mistake or an input error

Reply 2

OP

X^2 calc= (5-6.65)^2/6.65+ 〖(2-6.65)〗^2/6.65+〖(14-7.70)〗^2/7.70+〖(4-5.07)〗^2/5.07+ 〖(10-5.07)〗^2/5.07+〖(2-5.87)〗^2/5.87+〖(10-7.28)〗^2/7.28+〖(7-7.28)〗^2/7.28+〖(6-8.43)〗^3/8.43= 15.711

Reply 3

OP

Original post by rosiemoonlight

X^2 calc= (5-6.65)^2/6.65+ 〖(2-6.65)〗^2/6.65+〖(14-7.70)〗^2/7.70+〖(4-5.07)〗^2/5.07+ 〖(10-5.07)〗^2/5.07+〖(2-5.87)〗^2/5.87+〖(10-7.28)〗^2/7.28+〖(7-7.28)〗^2/7.28+〖(6-8.43)〗^3/8.43= 15.711

Sorry, took me a while as I was trying to attach as an image. the value I got on my GDC Was 18.118. My teacher did say there could be a small difference between the two values but I would need to research to work out why. I have had a look but cant find anything. perhaps something to do with precision.

Reply 4

Original post by rosiemoonlight

X^2 calc= (5-6.65)^2/6.65+ 〖(2-6.65)〗^2/6.65+〖(14-7.70)〗^2/7.70+〖(4-5.07)〗^2/5.07+ 〖(10-5.07)〗^2/5.07+〖(2-5.87)〗^2/5.87+〖(10-7.28)〗^2/7.28+〖(7-7.28)〗^2/7.28+〖(6-8.43)〗^3/8.43= 15.711

Can you add the question so I can check it properly.

Reply 5

19AAkmal

1

Original post by rosiemoonlight

I am currently doing the IB and working on my maths internal assessment. I have conducted a Chi squared independence test but my hand calculated chi squared calc value is different to the one on my GDC. Dose anyone know why this could possibly be?

dear sir what is this is it the homewok are days.

Reply 6

OP

Original post by 19AAkmal

dear sir what is this is it the homewok are days.

Sorry?

Reply 7

OP

Original post by Muttley79

Can you add the question so I can check it properly.

I don't have a question as I its an exploration. I am happy to check it myself but there is a possibility that there is a small difference in the values. what do you think this would be cause by?

Reply 8

Original post by rosiemoonlight

I don't have a question as I its an exploration. I am happy to check it myself but there is a possibility that there is a small difference in the values. what do you think this would be cause by?

So where did the 'observed' and 'expected' values come from? The two values are suspiciously far apart.

Reply 9

Original post by rosiemoonlight

Sorry, took me a while as I was trying to attach as an image. the value I got on my GDC Was 18.118. My teacher did say there could be a small difference between the two values but I would need to research to work out why. I have had a look but cant find anything. perhaps something to do with precision.

I see you have written cubed on the last one - this is where you've gone wrong :smile:

OP

Original post by Muttley79

I see you have written cubed on the last one - this is where you've gone wrong :smile:

Omg, Amazing! Thank you so much!!! Such a silly mistake!

Reply 12

OP

Original post by rosiemoonlight

Omg, Amazing! Thank you so much!!! Such a silly mistake!

Would you advise any other test to lengthen my IA and show ability? I have calculated spearmans rank and chi. Some others have taught themselves techniques to show mathematical engagement.

Reply 13

Original post by rosiemoonlight

Would you advise any other test to lengthen my IA and show ability? I have calculated spearmans rank and chi. Some others have taught themselves techniques to show mathematical engagement.

Sorry I know nothing about the assessment objectives - I only teach A level.

What about product- moment correlation coefficient? Line of regression? A bit hard to recommend without knowing more about the data - is it made up ?

Reply 14

OP

Original post by Muttley79

Sorry I know nothing about the assessment objectives - I only teach A level.

What about product- moment correlation coefficient? Line of regression? A bit hard to recommend without knowing more about the data - is it made up ?

I wanted to investigate whether hours of sleep required a night increases with age.

Reply 15

OP

Original post by rosiemoonlight

I wanted to investigate whether hours of sleep required a night increases with age.

because my graph is exponential I don't think it is advisable to do pearsons product moment. :smile:

Reply 16

Original post by rosiemoonlight

because my graph is exponential I don't think it is advisable to do pearsons product moment. :smile:

Surely that sort of discussion could be included?

Pearson's product moment correlation coefficient can be used when both variables being studied are normally distributed....

Reply 17

OP

I am not sure how to tell if my variables are normally distributed :smile:

Reply 18

OP

Can I use spearmans to calculate the line of regression to predict future values or do I have to use persons for this?

Reply 19

OP