# Part A1 of Paper 2

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Hey guys, I'm sure most of you'll are familiar with the Chi-square and t-test concepts, so just a small request? can you explain those to me, the usage, importance and need et all, so you know I revise my basics this way!

Or you could post a link too, choice is your, any help appreciated !

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Chi-squared is a dependency test. If chi is greater than the critical value then the null hypothesis is rejected, if chi is less than the critical value then the null hypothesis is accepted. There is also a high chance I reversed those so you might want that verified. I've never seen/done a t-test for biology (we didn't even do a chi-squared test actually...) so I wouldn't really worry about it.

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Chi-squared test isnt in the biology syllabus but the t-test is.

It doesn't come up often but if it does you wont need to know how to calculate it. I would assume you would be given a calculated t-value and a summarised table of critical values. You can figure out the degrees of freedom by adding the amount of trials from both variable then minus 2. Then you find the critical value for that degree of freedom and if the calculated t value is larger than the critical value, then there is a statistically significance difference in the results from the two variables.

I honestly only finally understood it when I had to use it in an IA, so if want, i would suggest you do a future IA where you can utilize the test as it really forces you to actually understand it even if it is a really easy concept to understand.

If you are still a bit confused, just google 't-test' and a few good websites will come up that will probably explain it a bit better.

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