Stats questions

Faith

I apologise in advance for asking what is probably a really stupid question to you guys, but stats + me = bad. I'm supposed to be doing a graph of the relative amount of something against time... but how do I calculate the relative amount? Say the following are the numbers:

100
89.6
82.2
76.2

Is that the relative amount, or do I need to do some working out?

Secondly, I'm supposed to plot a graph seeing if a volume decreases exponentially with time, how do I do that? I'm honestly hopeless with these kinds of things! I have GraphPad Prism and excel.

Thanks for any help!

2Scoops

If the values 89.6, 82.2, 76.2 are all relative to the 100 (as in "control = 100%") then all you need do is graph the numbers - they show the percent decrease relative to the control condition.

The same for the decreasing volume over time: express each subsequent volume as a percentage of the initial volume and graph these numbers.

Delphi91

As for the exponential fit, you could plot the figures in Excel and then get Excel to add a "trendline" to the graph - you can do this by right-clicking on one of the points that has been plotted. Pick "exponential" when you do this and if they're showing an exponential decay, then the line that Excel draws will go through most of your points. Have a look at the Excel file attached - I just made up the figures and have plotted the 100, 50, etc against 1, 2, 3, etc. I got it to print the equation of the trendline and as you can see it involves a negative power of "e", hence expontial (e) and decaying/decreasing (-)

Hope this helps.

ZorbaTehZ

(I'm not sure if this is what you've already said Delphi) You could also just right click on the y axis in the graph and under the scale tab check the box that says Logarithmic Scale which will give you a straight line.

Delphi91

ZorbaTehZ wrote: »

(I'm not sure if this is what you've already said Delphi) You could also just right click on the y axis in the graph and under the scale tab check the box that says Logarithmic Scale which will give you a straight line.

True!

Faith

Thanks a lot guys, that's really helpful!