# Statistics in biology Watch

Can someone please explain what do the following terms mean. I am really confused.I have tried looking them up on youtube etc but still not sure.

Student's t-test(also critical value and especially 95 % confidence limit(just cant understand that for some reason))
Chi-squared test

2. Hey there, welcome to TSR

The Student's T-Test is used when comparing the mean values of two sets of data. It is used to see whether or not the two means are significantly different.
So to find a critical value for the T-Test, you calculate something called the "degrees of freedom". This is done by doing (n1 + n2) - 2 where n is the amount of values. There will be a reference table given in the exam if there is a question on it where you lookup the degrees of freedom that you calculated and next to it will be the corresponding critical value.

If the T-Test value you calculated is GREATER than the critical value then you REJECT the NULL HYPOTHESIS. Rejecting the null hypothesis means that there is less than 5% probability that the results gathered are due to chance, so therefore you are 95% certain that the results are not due to chance.

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.

Hopefully this helps
3. reallly helped thanks a lot

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