Should I use the Spearman's Rank Correlation Coefficient test in this experiment?

[arnab]

Hi

I recently did a enzyme-inhibition experiment for my unit 6 coursework and i am now on the part where i have to carry out a statistical test on the data i collected from my experiment. This is what my experiment was bascally about :

 

 

It was just a simple enzyme-inhibition experiment. SO in a simplifed version :

 

1. I first poured 5cm3 of milk in to 4different test tubes

2. To another set of 4test tube, I then added 2cm3 of trypsin to each of them and then adden 1cm3 of the inhibitor at a concentration 10-4 mol dm^3.

3. I then poured the solution containing the enzyme trypsin and inhibitors into the milk

4. I then took reading for the Absorbance value from the colorimeter, at a regular interval for 15second for the next 4minutes.

5. I then repeated the experiment but with different concentration of the inhibitor, i.e 10^-3 mol dm^3 & 10^-2 mol dm^3

 

Now i was thinking of using the spearman'r rank correlation Coefficient to determine a relationship between the absorbance value for different inhibitor concentration but i am unsure as to how to go about doing it.

 

Am i right in understanding that i should i just use Absorbance values I collected for the lowest and highest concentration of inhibitor in order to determine there is a relationship between the different concentration of inhibition?

 

Or am i completely wrong in using this statistical test? PLEASE ADVICE!

Edited May 3, 2012 by arnab

[ecoli]

The more usual thing to do, I believe, is a parametric method, such as linear correlation, to compute a model of how inhibitor effects absorbency readings. Though if the function isn't linear, you might need a fancier catalytic model, such as Michaelis-Menton.

[arnab]

The more usual thing to do, I believe, is a parametric method, such as linear correlation, to compute a model of how inhibitor effects absorbency readings. Though if the function isn't linear, you might need a fancier catalytic model, such as Michaelis-Menton.

 

so you mean to say, i should be looking to do a MANN-WHITNEY U test?

[ecoli]

so you mean to say, i should be looking to do a MANN-WHITNEY U test?

 

Mann whitney is a nonparametric method for hypothesis testing between two samples. So I'm not sure how you got that from what I said.

 

I suggest a parametric method to model the correlation: such as linear regression. If the data doesn't look linear, than we can talk about that, too.

[arnab]

Mann whitney is a nonparametric method for hypothesis testing between two samples. So I'm not sure how you got that from what I said.

 

I suggest a parametric method to model the correlation: such as linear regression. If the data doesn't look linear, than we can talk about that, too.

 

Sorry i am panicking a bit at the moment. I had no idea i had to do a statistical test for my coursework and its due in tomorrow!

 

My data does show a linear regression. So as the concentration of the inhibitor increases, the absorbance also increases, hence showing the rate of reaction decreases. Also seen by the fact that the milk went "less clear". I was originally thinking of using the Spearman rank coefficient test, but then i have no idea as to how see my data is within the 5% confidence level :/

 

What could be your advice, to use the spearman rank test or something else?

Edited May 3, 2012 by arnab

[ecoli]

read this: http://stattrek.com/regression/slope-test.aspx

 

Correlation metrics are measuring how the data trends together, and is not a method for hypothesis testing. Linear regression is related to correlation, but is a model fitting technique. But because its a parametric method, you can use possible variance in those parameters to test a hypothesis (in this case, the null hypothesis)

 

And here's how to do a simple linear regression in MS excel: http://www.ncsu.edu/labwrite/res/gt/gt-reg-home.html

[arnab]

read this: http://stattrek.com/...slope-test.aspx

 

Correlation metrics are measuring how the data trends together, and is not a method for hypothesis testing. Linear regression is related to correlation, but is a model fitting technique. But because its a parametric method, you can use possible variance in those parameters to test a hypothesis (in this case, the null hypothesis)

 

And here's how to do a simple linear regression in MS excel: http://www.ncsu.edu/...t-reg-home.html

 

Thanks for your help i have decided that i am going to use the spearman rank coefficient test for my data + plus calculate the standard deviation and the mean. I hoping from the standard deviation and the mean, i could be able to determine the "95% confidence level test" thing lol. Sorry but my english is not good