# Statistics in biology

Announcements Posted on
Four hours left to win £100 of Amazon vouchers!! Don't miss out! Take our short survey to enter 24-10-2016

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

## Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank
2. this can't be left blank
3. this can't be left blank

6 characters or longer with both numbers and letters is safer

4. this can't be left empty
1. Oops, you need to agree to our Ts&Cs to register

Updated: May 20, 2016
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Today on TSR

### Who is getting a uni offer this half term?

Find out which unis are hot off the mark here

### How to get a 1st class degree

Poll
Useful resources
Study resources

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.