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

Homework Help: Two-Sample Problem STAT Help!

  1. Apr 26, 2010 #1
    1. The problem statement, all variables and given/known data

    Do birds learn to time their breeding? Blue titmice eat caterpillars. The birds would like lots of caterpillars around when they have young to feed, but they breed earlier than peak caterpillar season. Do the birds learn from one year's experience when they time breeding the next year? Researchers randomly assigned 7 pairs of birds to have the natural caterpillar supply supplemented while feeding their young and another 6 pairs to serve as a control group relying on natural food supply. The next year, they measured how many days after the caterpillar peak the birds produced their nestlings.

    Did the randomization produce similar groups? First, compare the two groups in the first year. The only difference should be the chance effect of the random assignment. The study report says, "In the experimental year, the degree of synchronization did not differ between food-supplemented and control females." For this comparison, the report gives t=-1.05. What type of t statistic (paired or two-sample) is this? Show that this t leads to the quoted conclusion.

    2. Relevant equations

    I'm not sure..

    3. The attempt at a solution

    First off, I'm not sure what it means when it says to compare the groups. I'm pretty sure it's a two-sample problem. I'm also not sure of how to do the rest of the problem either. A little push in the right direction would be greatly appreciated! :)
  2. jcsd
  3. Apr 26, 2010 #2
    I'm pretty sure this isn't right, but this is what I tentatively have down:

    The two groups in the first year did not differ at all. “In the experimental year, the degree of synchronization did not differ between food-supplemented and control females.” The t statistic -1.05 is a two-sample statistic. Since -1.05 does not lie on the chart of Table C for degrees of freedom=5, we know that m1=m2, which means that the synchronizations didn’t differ between the food-supplemented and control females, just like the experimenter said.

    Help would be awesome!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook