Null versus Alternative Hypotheses
Form groups of 4-5 and perform a selection experiment of sorts. First you might ask what the heck do beans have to do with behavior? Sinervo is loosing it. We shall soon see.
Count out a pile of 200 black beans.
Then designate one member of the group as the bean picker. The other members of the group can weigh out the piles of beans as they are collected, and then record and graph the data for the group.
The bean picker will pick approximately 5-10 between their thumb, index, and forefinger and gently roll around the beans and let some beans spill out until only one bean remains. Take this bean and set it aside in "lot 1". Repeat this procedure with the remaining pile of beans 9 more times so that you end up with 10 beans in lot 1.
Set aside lot 1 and have some of the members weigh out lot 1, while the bean pickers continues making lots 2, 3, ..., 20 by the same procedure. Each lot has 10 beans in it.
Let us first set up a null hypothesis. What pattern of bean size
would you predict if you were randomly drawing beans from the pile as a
function of size.
Recall the manner in which you collected data on beans.
Let us now set up an alternative hypothesis. What kinds of patterns
might you predict if the drawing was in some way non-random. Describe mechanisms
that might explain these patterns. You might in fact have one or more alternative
hypotheses to test. You should try to describe at least two hypotheses,
and two mechanisms. Discuss the null and alternative hypothesis amongst
the members of the group.
Graph the data that your group obtained on bean size as a function of
lot# (e.g., 1 is the first lot, 2 is the second lot, etc.). If some member
of the group knows how to use a simple graphing program it might be useful
to plot the data on the computer (and get copies of the graphs to other
members of the group). If some member of the group knows how to run a simple
linear regression, even better! Run a regression line through the data.
What is the pattern of size change that is found in your samples of beans from the first draw to the last draw?
Is this pattern statistically significant? Do we reject or accept our null hypothesis?
How can you explain this pattern in light of your alternative hypotheses?
The Big Picture Question. What sort of implications does this simple experiment have for the origins of Agriculture and cultivated plants? Refer to the paper by C. Heiser (available on reserve in the library) in your discussion of the been experiment. Now make some brief observations on the behavior of a living creature (any creature will do). Observe its movements, or perhaps its feeding behavior. Make a simple hypothesis concerning either:
Include your hypotheses concerning the creatures behaviors in the discussion.
Make a simple statement about the "unconcious aspects of natural selection"
in your lab report discussion.
Lab report (1 page with 1 page figure) is due 4/17.
Include the answers to all of the above Big Picture questions in the
form of a standard scientific report (see the Lab
Report web page for more details, as what is listed below is only a
brief summary):
Be succinct and to the point when writing your lab report!