# Experiment set up and data

Each group was given an orientation arena and told to set 0 towards the front of the room. They were then assigned a location to place their lamp at. For example, groups assigned 0 set their lamps at the top of the arena, while groups assigned 180 set their lamps at the bottom of the arena. This was done to try and eliminate any directional bias in the room.

The groups’ lamp assignment:

Group Lamp.Location
One 0
Two 50
Three 90
Four 140
Five 0
Six 230
Seven 270
Eight 320

The groups then each released the isopods individually in the center of the arena. They collected data on three “experimental” animals which were run with the lamp turned on, and two “control” animals with the lamp turned off. They measured the angle at which the animals crossed the edge of the arena, with respect to the front of the room. To get the angle with respect to the lamp, the students subtracted the angle where they measured the animals cross the arena from the angle position of their lamp. The numbers shown below are the student’s adjusted results, corrected to be with respect to the lamp position. To get the uncorrected version, simply add the group’s lamp location to the reported measurement.

The data:

Group Lamp.Location Exp.1 Exp.2 Exp.3 Cntrl.1 Cntrl.2
One 0 180 100 180 120 90
Two 50 130 210 70 120 170
Three 90 130 230 170 60 50
Four 140 160 -145 90 100 70
Five 0 170 130 -90 90 100
Six 230 20 120 80 30 10
Seven 270 -240 -95 -50 -270 60
Eight 320 -220 -290 NA -100 -300

# Experiment Analysis

Here we show the class’s data plotted, with the corresponding statistical tests for their experimental group (with respect to the lamp, and then again with respect to the front of the room), and the control group (with respect to the lamp, and then again with respect to the front of the room). We end with a watson’s two test comparing the experimental and control group.

## The Experimental group, Relative to the lamp

If the animals had phototaxis, they would be oriented relative to the light here (where the light is at 0)

## $Rayleigh Test P-value ## [1] 0.0064683 ## ##$Mean Angle
## [1] 2.544426
##
## $Mean Resultant Vector Length ## [1] 0.4601774 ## The Experimental group, relative to the front of the room This orientation should be random. If not, it indicates there is a directional bias in the room itself ##$Rayleigh Test P-value
## [1] 0.3125656
##
## $Mean Angle ## [1] -2.366986 ## ##$Mean Resultant Vector Length
## [1] 0.2259028

## Control Group, Relative to the lamp

If the animals were not being influenced by the presence of the lamp itself, this orientation should be random. If not, it indicates the animals had a prefered direction they liked to move relative to the lamp, regardless of whether it was turned on. The lamp is at 0.

## $Rayleigh Test P-value ## [1] 0.0001978523 ## ##$Mean Angle
## [1] 1.403986
##
## $Mean Resultant Vector Length ## [1] 0.6888091 ## The Control group, relative to the front of the room This orientation should be random. If not, it indicates there is a directional bias in the room itself ##$Rayleigh Test P-value
## [1] 0.3575454
##
## $Mean Angle ## [1] 3.01729 ## ##$Mean Resultant Vector Length
## [1] 0.255507

## A Watson two-test to see if the direction of orientation for the experimental group and the control group (relative to the lamp) are the same

See slides for more details on what a watson two-test is.

watson.two.test(Experimental.Corrected,Control.Corrected)
##
##       Watson's Two-Sample Test of Homogeneity
##
## Test Statistic: 0.214
## 0.01 < P-value < 0.05
##