A question regarding t-test and chi-squared test

[idrees]

Hey, hope you all are doing fine.

Okay, so I know how to perform the two tests but the part I'm struggling with is interpreting the results of the t-test and the chi².
The farthest I can go with my explanation is to state whether the result is significant or not. I know .. not so great. Well. the usual questions following the test, regardless of the context
(i) Significance of the t value using the critical value (wth is the critical value)
(ii) Explain the result in terms of probability table
(iii) reliability of result
(iv) ref. to standard deviation?

I am so clouded. could you help clear at least some of the doubts?
Thanks

[MKh]

so is this from CIE or edexcel..i thnk CIE....well I take edexcel...v do not have to carry out the tests and interpretting results is a bit different in Edexcel...do u study in a school? If yes, ask ur teachers to help, buddy...gud luck....

[Sue T]

actually its 4 both cie and edexcel - cuz my cie class got the notes 4 ths from the edexcel class - will take a while2 scan though... will upload asap

[Master_Key]

actually its 4 both cie and edexcel - cuz my cie class got the notes 4 ths from the edexcel class - will take a while2 scan though... will upload asap

If you have CIE A level Biology then switch on to the end of book before the answers. T-Test samples and explanation is given.

[Sue T]

yes but some ppl (like me) have A2 Biology < ths txt book dsnt have that - anyways heres wat i said ill attach

[Sue T]

2

[Sue T]

there r just a few xtra things - ull b able 2 point out wat is not really needed - but ive tried 2 only scan th impo parts

[MKh]

ohhh thnxx buddy..u r soo helpful!!! +repz 4 u!! where did u get all this from??? this is so helpful...have anything else that is important? If yes, plz do post..Thanks again!

[Sue T]

nope - everythin else i have i got from asking on this forum  - welcom

[Book lover22]

my question regarding these statistical tests is:

How do we knw wat significance level to take like 5% or 10%? this is asked wen we have 2 compare our calculated value wid da critical value!
What is degree of freedom? like 18 degrees of freedom?

Thankuss!

[poisonedrose]

We usually take 0.05/5% as being the critical one.
To calculate the degrees of freedom, simply calculate the (number of classes of data-1)
So if you have 19 classes of data/19 possible sets of phenotype, then the degrees of freedom in this case would be 18.

[MKh]

ohhh thnk u dear and what is classes of data??

[poisonedrose]

Classes of data are basically the number of phenotypes or the number of data sets you have.
Like, for example if your experiment is the difference between the reaction time of females and males, the number of classes of data is 2. So the degrees of freedom, in this case, would be one.

If you took purple strems, cut leaves: purple stems,potato leaves: green stems,cut leaves: green stems,potato leaves( like you would for a dihybrid cross), then there are four classes of data. So the degrees of freedom is 3.  =)

[MKh]

ohh thnk u sooo much!