Biological Data Analysis: Homework 2

Due Thursday, Sept. 8


You must type this and all other homework assignments. Do not e-mail the assignment to me; turn it in early (at 322 Wolf) for a foreseeable absence, or turn it in late after an unexpected absence from class.


1. Get five coins and put them in a container with a lid, so that you can flip all five coins at once by shaking the container and then letting the coins fall to the bottom. If you flip the five coins, and the probability of one coin being "tails" is 0.50, what is the probability of getting "tails" on all five coins?

2. Now you are going to do an experiment to see whether thinking about tails makes tails more likely to appear. You will think about tails, shake your coin container, and see how many tails you get. What is the biological null hypothesis? The biological alternative hypothesis? The statistical null hypothesis? The statistical alternative hypothesis?

3. Now do the experiment. Think about tails, flip your five coins, and record how many tails (0 to 5) you got.

4. If you got five tails in question 3, skip question 4 and just answer question 5. If you didn't get five tails, maybe you just weren't doing the experiment right. So work your way down this list, record the number of tails for each experiment, and keep going until you get five tails, then stop and go to question 5. Turn in a table of your results, with rows labelled "a" through "o" and one column for each condition (if you have to shake longer, etc.). Also turn in your drawings, if you get that far.

  1. Think about the word "tails" while you flip the coins.
  2. Look at the word "tails" on your computer screen while you flip the coins.
  3. Write down the word "tails" and look at it while you flilp the coins.
  4. Hmm, maybe it needs to be in all caps. Think about the word "TAILS" while you flip the coins.
  5. Look at the word "TAILS" on your computer while you flip the coins.
  6. Write down the word "TAILS" and look at it while you flilp the coins.
  7. Hmm, maybe it's not the word "tails" you should think about. Imagine the tail side of one of the coins you're flipping while you flip the coins.
  8. Get an extra coin, put it tail-side up where you can see it, and look at it while you flip the coins.
  9. Draw a picture of the tail side of your coin and look at it while you flip the coins.
  10. Hmm, maybe you need to think about five tails to get five tails. So imagine the tails side of five coins while you flip the coins.
  11. Put five coins tail-side up where you can see them and look at them while you flip the coins.
  12. Draw the tail side of five coins and look at the drawing while you flip the coins.
  13. Hmm, maybe you need to be more literal about "tails". Think about an animal with a tail, and imagine its tail while you flip the five coins.
  14. Do a Google image search to find a picture of your animal's tail, and look at it while you flip the coins.
  15. Draw a picture of your animal's tail and look at the drawing while you flip the coins.
  16. Maybe you weren't shaking the coins hard enough. If you still don't have five tails, do the above experiments (a through o) over again, only this time, shake the coins harder. Stop once you get five tails, of course.
  17. If you still don't have five tails, change something else about the conditions and do the above experiments (a through o) over again; maybe use nickels instead of pennies, or stand up instead of sitting down, etc. If after all that, you still don't have an experiment with five tails, change something else about the experiment; keep doing this until you get five tails.

5. Based on the results of your last experiment (the one that gave you five tails), what would a stupid or evil biologist conclude?

6. You're not stupid or evil (I hope), so what do you conclude?


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This page was last revised August 23, 2016. Its URL is http://udel.edu/~mcdonald/stathw2.html