I did a biology experiment and I have to use the chi^2 method to calculate statistical significance. I got data at different time points and I just want to make sure what I'm calculating this right. The data I got for one time point are 6 and 23 I know the equation for chi^2 is
chi^2= (obs-exp)^2/exp I calculated my expected value by taking the average of the ones I have, I got 14.5. Will my observed value be any of the two I have, or do I have the add them and that will be my observed value?
Actually, I am wondering what you are doing. Chi squared is used to
a) see if a frequency distribution is close to some expected
b) to test the independence of two distributions.
The issue I have is how did you get two data for one time? Are these representative of the same data, or are you comparing two sets to see if independent (statistical significance maybe).
So I need a description of what you are trying to measure, and what you are doing with it.
I did a biology experiment where I need to analyze the statistical significance of betweeen a data set. My experiment consisted of measuring the effects in photosynthesis and cellular respiration by exposing solutions with leaf discs to different light wavelength. For the statistical significance, I have to compare data I got with blue and green light to white light. The amount of discs for the time point I chose for blue was: 3, white: 23 and for green: 6 I'm supposed to use the chi square method to compare this values and I got 13 for my expected value between blue and white and 8.5 between green and white and then a chi square of 7.69 for blue/white and of 24.735 for green/white. Are those values right? I have to use this method for many other time points but if I have this one right probably I have the others right, same if I have it wrong, if they are wrong, please explain how to calculate it. Thanks
To calculate the chi^2 statistic using the equation chi^2 = (obs-exp)^2/exp, you will need both the observed and expected values for your data.
In your case, if you have only two observed values (6 and 23) from one time point, you would calculate the chi^2 statistic for each individual observation and then sum them up to get the final chi^2 value. You do not need to add the observed values together to get a single observed value.
Here's how you can calculate the chi^2 statistic for each observed value:
For the observed value of 6:
chi^2_1 = (6 - 14.5)^2 / 14.5
For the observed value of 23:
chi^2_2 = (23 - 14.5)^2 / 14.5
Once you calculate chi^2_1 and chi^2_2, you can sum them up to get the final chi^2 value:
chi^2 = chi^2_1 + chi^2_2
This final chi^2 value will be used to determine the statistical significance of your data. You would compare this value with the corresponding critical values from the chi^2 distribution table or use a statistical software to calculate the p-value associated with the chi^2 value.
Remember, the chi^2 test assumes certain assumptions, such as independence of observations and a large enough sample size. Make sure to check if these assumptions hold for your data before interpreting the results.