Variables
Ola, my wonderfully eager scientists.
I'm back to the grind, and missing you guys like crazy! Theres a few new Queen's students that are going to Power and Im soooo jealous
As for asking me questions about bio, that's what it's is for :) I don't mind it at all... it's a nice break from writing about my philosophy about education.
aanyhoo, on with variables
As you know, variables are the things that can change, so the temperature of a substrate or the level of sweating by a participant.
There are the two different types of variables, Dependent and independent(or controlled). Take a look at the words and that'll give you the clue as to what they are.
the Independent variable is the one that is self-determining... you manipulate/change this one.
the Dependent variable is the one that is...dependent on the independent variable.
So, to give you an example, I invented a drug and wanted to test the dosage and how this effects the sweat response in the body.
The amount of the drug administered is the independent variable and the response is the dependent variable. Does that make sense? The sweat response is illicited by the drug, you need the drug to cause the sweating.
Another example?
The caffiene you administered would be the independent variable because you are the one controlling the outcome.
The heartrate is the dependent variable because it's the one you can't control... it is changed by the amount of drug in the bloodstream.
If you've got any more questions, drop me a line
:D
happy labbing!
posted by Ms. Tenn-ilicious @ 3:58 p.m.
2 Comments:
umm miss i know this is kinda late now but what's the significance if the t-value is higher or lower when you compare them?
i found some info that might be useful from a site:
Student's t-test
Definition: It is the statistical test used to evaluate if two groups are significatively different according to their means.
Hypothesis: The null hypothesis of a t-test always proposes that the two groups do not differ significatively, whilst the hypothesis of a t-test always proposes that there is a difference.
Why you use it: The t-test is used to prove or to discard the mentioned null hypothesis of difference.
To do it you must obtain two data:
The t value (t).
The df value degrees of freedom (df)
You already know all symbols but one:
v = variance
Once you have your "t" and "df", first you have to check your t-Distribution Table (it is at the end of this document), where you must find the "df" column which has to be equal to what you calculated or the nearest one.
Second, you must look at the level of confidence column that you wish to work with. The most commonly are 0.05 and 0.01. (The 0.05 means that in a 95% the groups will differ significatively and there is a 5 % of possibilities of error).
If your calculated "t" value is bigger than the value of the table, you reject the null hypothesis. If the value is smaller, you accept the null hypothesis.
> rejects the null hypothesis.
< accepts the null hypothesis.
Special considerations:
The t-test may be used to compare the results of one experiment with the results of another experiment conducted on different times.
The t-test may also be used to compare means of one same group in two different moments.
The t-test may be used to compare means of two different groups or variables, at the same moment.
--------------------------------------------------------------------------------
T-Test T Student Distribution Table
Degrees of Freedom Level of Confidence (0.05) Level of Confidence (0.01)
---------------------------------------- ---------------------------------------- ----------------------------------------
1 6.3138 31.821
2 2.9200 6.965
3 2.3534 4.541
4 2.2328 3.747
5 2.0150 3.365
6 1.9432 3.143
7 1.8046 2.998
8 1.8595 2.896
9 1.8331 2.821
10 1.8125 2.764
11 1.7959 2.718
12 1.7823 2.681
13 1.7709 2.650
14 1.7613 2.624
15 1.7530 2.602
16 1.7459 2.583
17 1.7396 2.567
18 1.7341 2.552
19 1.7291 2.539
20 1.7247 2.528
21 1.7207 2.518
22 1.7171 2.508
23 1.7139 2.500
24 1.7109 2.492
25 1.7081 2.485
26 1.7056 2.479
27 1.7033 2.473
28 1.7011 2.467
29 1.6991 2.462
30 1.6973 2.457
35 1.6896 2.438
40 1.6839 2.423
45 1.6794 2.412
50 1.6759 2.403
60 1.6707 2.390
70 1.6669 2.381
80 1.6641 2.374
90 1.6620 2.368
100 1.6602 2.364
120 1.6577 2.358
140 1.6558 2.353
160 1.6545 2.350
180 1.6534 2.347
200 1.6525 2.345
Infinite 1.645 2.326
This is the site: http://www.cem.itesm.mx/profesores/dp/eleon/t-test.htm
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