Burden, Sierra, Animal Behavior, Tuesday C, Pset

# Burden, Sierra, Animal Behavior, Tuesday C, Pset - Bio 44Y...

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1 Bio 44Y - Spring 2011 Animal Behavior Name: Sierra Burden CA/Intern: Taryn and Katrina Lab Partner: Animal Behavior Statistics Problem Set (5 points) Overview: This worksheet will review the Z-test and the T-test, which you learned in 44X, and will also introduce you to another common statistical test called the G-test that may be useful for analyzing your data. The equations and tables for all three of these statistical tests are included in the lab manual. There are three calculation-based problems. Read the example, then perform the analysis on your own. Definitions and uses of the various tests: Z-test : used to compare independent proportions Data type: yes/no variable (e.g., germinated seed / ungerminated seed, ant touched / did not touch food) Theory: The Z-test will find the difference between measured proportions for each of these two groups and then determine the probability that the difference between the two proportions occurred solely by chance (i.e., there is something other than chance that makes the outcomes so different). T-test: used to compare independent means Data type: continuous variable (e.g., average number of ants per 5-minute interval that touched food) Theory: The T-test compares the difference in sample means. A large value given by the T-test suggests that the group means differ by an amount that cannot be explained solely by chance. G-test: used to assess evenness-of-fit (i.e., for distributions) Data type: yes/no (e.g., ant in location / not in location) Theory: The G-test compares expected even frequencies / distribution / outcomes to those observed. (You may also use the X 2 -test, if you are familiar with it, but since the other three tests may be used for the same experiments, we will not be covering it here.)

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2 Bio 44Y - Spring 2011 Animal Behavior Example 1: The Z-test Oleic acid elicits necrophoric behavior in some ant species. Small pieces of paper treated with this substance are carried by workers to the midden pile as if they were dead ants. Taryn and Katrina want to test the effects of different concentrations of oleic acid on the necrophoric response. In each trial, they place in one corner of the tank a small pile of identical paper pieces that have been treated with one concentration of oleic acid. They use a different concentration of oleic acid for each trial. Thirty minutes after the start of a trial, they observe the proportion of paper pieces that have been transported from the pile to the midden. Taryn and Katrina now want to compare the 3/20 untreated control pieces that were relocated to the midden in Trial 1 with the 12/24 pieces treated with 1 mg/ml oleic acid that were moved to the midden in Trial 2. 1.
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## This note was uploaded on 09/19/2011 for the course BIOLOGY 44Y taught by Professor Smith during the Winter '11 term at Stanford.

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Burden, Sierra, Animal Behavior, Tuesday C, Pset - Bio 44Y...

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