Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Using t-tests to get trials until significance ?

  1. Jul 1, 2010 #1
    Using t-tests to get "trials until significance"?

    Hi all,
    I am stumped on how to achieve this with the data I have. My PI thinks there is a way, but I can't seem to find it. We want to see whether we should go ahead with this experiment or if it will take too much time.

    Basically, I have 2 sets of data. I am looking to see which one conforms to a logarithmic regression line better, i.e. which one has better fit. To do that, I checked the r^2 values, and then did a t-test for unequal variance on the residual sum of squares. The difference was miniscule (p=.73).

    Now, what I have at the moment is the formula for the t-test for unequal variances:
    t=(xa-xb)/sqrt((sa+sb)/n)

    where xa and xb are the sample means, sa and sb are the sample variances, and n is the number of trials (the actual formula uses sa/na + sb/nb, but I have the same number of data points for each set of data)

    I manipulated it to show how many trials I need until t=1.96 (basically just close to significance)
    n=(sa+sb)/((xa-xb)/t)^2

    The issue I have with this, though, is that the means and variances could be different. How can I use this to calculate the estimated number of trials when the data I have may not be accurate? Is there even a way to do this?
    Thanks for any help.
     
  2. jcsd
  3. Jul 2, 2010 #2

    EnumaElish

    User Avatar
    Science Advisor
    Homework Helper

    Last edited: Jul 2, 2010
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Using t-tests to get trials until significance ?
  1. To F test or T test (Replies: 1)

  2. Power of a t-test (Replies: 1)

Loading...