How to read the table values of t in t-test?

[rethna30]

Hi guys,

I'm not clear with t-test. I've tried reading the CIE text book "Statistics" part. Yet, I don't understand what is t-test for? What is null hypothesis? When the t-test should be used? How to read the table values of t in t-test?

Thanks in advance....

 

[Ayesha]

T-test, basically, is a comparison test between means of two sets of data which are said to be following a normal distribution. For e.g: O/N'07 Q3: We have to find out if grazing effects the population of the rare moth species. Right....

Step 1: We will assume that grazing DOES-NOT effect moth population----This is called a null hypothesis; u reject diff. b/w 2 sets of values.
Step 2: We will do the t-test, and match the value with the critical value table. If the value in the table at p< 0.05 is less than our calculated value, then that
means your confidence % is probably even less than 5%.
Step3: Your conclusion is that as the confidence % is less than 0.05(the critical probability), the null hypothesis u proposed has been rejected, Right......?
This means that grazing of land DOES effect moth population.....

Hope that helped, another e.g. of null hypothesis is in O/N '09. Can't tell which 1 bcoz i have to go study . Best of Luck!!!

 

[rethna30]

@Ayesha...

Thanks so much...But, I have another question....is Chi-Square related to t-test? Coz, in that question they are asking for chi-square right? But, in text book, they said t-test differs from chi-square...and they have different tables...

 

[Ayesha]

I am not v.sure but as far as I know there isn't a link at least they have not asked any such thing in Past papers. T-test compares normal distribution data while Chi-squared test compares discontinuous data. Quite the opposite!

U're soo right I had completely forgotten they had used chi-squared value, nevertheless after the t-test or chi-squared value has been calculated, it has to be treated in the same way using their RESPECTIVE tables. (the tables for these two statistical tests are NOT the same)

 

[Zohaib Sherazi]

Chi-square test is applied on discontinuous data. While the t-test is for continuous data.

 

[rethna30]

Thank you guys!!! Was really helpful....

 

[zahraahmed]

http://notezone.net/cambridgechem/chemi ... sis%5D.pdf can sum1 go in dix page 11 n do solve n gimme answers plzzzz i cant able to slove it n it might cum for exam help mee!!!!

 

[filza94]

http://notezone.net/cambridgechem/chemi ... sis%5D.pdf plz go dix link pg 11 n c answers below of it

First of all you need the mass of FA1. In the first table you have the mass of the empty test tube and the

mass of the test tube + FA1. All you do is subtract the values 12.80 - 10.50 giving you 2.30g of FA1.

In the second table you need the mass of FA1 after heating. Again, you just subtract the values 11.76 -

10.50 = 1.26g FA1 after heating.

1 d. (i) The mass of anhydrous XS04 present in the crystals is what is left over after heating = 1.26g

1 d. (ii) The mass of water driven from the crystals is the loss in mass that has occurred when the FA1 was

heated. Before heating there were 2.30g of FA1 and after heating there were 1.26g. So the mass of water

lost is 2.30 - 1.26 = 1.04g

1 e. To calculate the number of moles of water in the sample of FA1 you use the formula no. of moles =

mass/mass of 1 mole which gives you 1.04/18 = 0.058 mol

1 f. The number of moles in XSO4
7 moles of H20 gives 1 mole XSO4 (from the formula XSO4.7H20)
So 0.058 moles of water give 0.058/7 = 8.29 x 10 ^ -3 moles of XSO4

1 g. To calculate the relative formula mass of XSO4 you use the formula mass of 1 mole = mass/no. of

moles which gives you 1.26/8.29 x 10 ^ -3 = 152.7

1 h. To calculate the Ar of element X you first find the Mr of SO4 which is 32 + (4 x 16) = 96
You subtract this from the RFM from part g giving you 152.7 - 96 = 56.7