Holcombe:CircularStatistics

SUPA Sydney University Perception and Action Lab Primer editing help refcard

Data is sometimes circular, like angles for direction selectivity and orientation selectivity. Most scientists are familiar with the normal distribution, and its standard deviation (σ) is used frequently to quantify the spread of a distribution. Sometimes we would like to compare a distribution on a circular variable to one on a non-circular variable. In our case people report the position of a blob revolving periodically about fixation. Histogram of the data shows the distribution of times corresponding to positions reported. We would like to estimate the standard deviation of the process that yields the variability in time. For instance there may be variability in when the observer samples the position, perhaps following a normal distribution. This would be non-circular mechanism whose results end up wrapped into circular form in our data.

Table uses distributions of 10.000 numbers and the c.i. calculated using 1.000 distributions.