# Edexcel AS Biology (new 2015 spec) - Chi-Squared Test?

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1. I am so confused by the Chi-Squared Test!! How likely is it to come up in the exam tomo?
2. (Original post by Philip-flop)
I am so confused by the Chi-Squared Test!! How likely is it to come up in the exam tomo?
Do we even need to know that? I was told by my teachers that you did not need to know that for the AS exam.
3. (Original post by aj122)
Do we even need to know that? I was told by my teachers that you did not need to know that for the AS exam.
Are you for definite? I just want to make sure. I'm so worried I don't know what to expect
4. The Chi-squared test is used when data is categoric and it is used to calculate the difference between the OBSERVED and EXPECTED details. It relates the number of individuals in particular categories and the calculation creates something called a "chi squared" value. The HIGHER the "chi squared" value calculated, the GREATER the difference between the observed and the expected results. Again, degrees of freedom can be calculated here (n-1) with n being the number of categories. Again, there will be a reference table and IF THE CHI SQUARED VALUE IS GREATER THAN THE CRITICAL VALUE then you REJECT the null hypothesis which shows that the probability that the results are due to chance is 5% or less AND THEREFORE this means THERE IS A CORRELATION BETWEEN THE DATA.
5. (Original post by CrazyFool229)
The Chi-squared test is used when data is categoric and it is used to calculate the difference between the OBSERVED and EXPECTED details. It relates the number of individuals in particular categories and the calculation creates something called a "chi squared" value. The HIGHER the "chi squared" value calculated, the GREATER the difference between the observed and the expected results. Again, degrees of freedom can be calculated here (n-1) with n being the number of categories. Again, there will be a reference table and IF THE CHI SQUARED VALUE IS GREATER THAN THE CRITICAL VALUE then you REJECT the null hypothesis which shows that the probability that the results are due to chance is 5% or less AND THEREFORE this means THERE IS A CORRELATION BETWEEN THE DATA.
Thank you for the great explanation!!
Do we need to know how to use the formula for the exam tomo?
6. (Original post by Philip-flop)
Thank you for the great explanation!!
Do we need to know how to use the formula for the exam tomo?
I do the AQA Specification for AS Biology so I'm not sure about Edexcel.

For AQA we don't need to know the calculations.
7. (Original post by Philip-flop)
Thank you for the great explanation!!
Do we need to know how to use the formula for the exam tomo?
No, we shouldn't. It's not in the specification. However, Edexcel would be allowed to put it in the paper, they'd just get a load of angry teachers phoning them up to complain. But it's not that difficult to familiarise yourself, and if they do put it in the exams they won't expect you to know the equations and will provide it to you.
8. It is in the spec actually right at the bottom under Maths Skills, not that hard though.

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