tag:blogger.com,1999:blog-6116727798952891296.post5941343600510451181..comments2019-08-15T18:48:20.423-07:00Comments on Doing Natural History: Are Daylilies Invasive?Aleta Karstadhttp://www.blogger.com/profile/15900113759159760493noreply@blogger.comBlogger1125tag:blogger.com,1999:blog-6116727798952891296.post-87654605068534793002019-08-15T18:48:20.423-07:002019-08-15T18:48:20.423-07:00Appendix 1 - Matt Keevil comments on the equality ...Appendix 1 - Matt Keevil comments on the equality of means and standard deviations of the distances between stands: "Well, I'm not sure what to make of equal mean and standard deviation except that I can't immediately come up with a reason that it shouldn't occur in a number of distributions. In the Poisson distribution the mean and the variance are defined as equivalent. I think that mechanistically a good candidate distribution is the exponential. The exponential is a case of the Gamma Distribution and describes inter-event times. Distance and time can be equivalent if we imagine taking observations while traveling at a constant speed so the rate at which Day Lilies go by might well be best described using an exponential distribution. For the exponential there is only one parameter, the rate parameter λ. The mean is 1/λ and the variance is 1/λ^2. I calculated lambda independently for each of the mean and sd for the three surveys. If the exponential is a good fit than presumably both calculated λ values based on the mean and the variance should be similar for each survey. This is indeed the case for 21 July (0.000979 vs 0.000895) and 24 July (0.000395 vs 0.000392). 2 August is a little more different, but not wildly dissimilar (3.24E-5 vs 5.56E-5) and in that case the sample size is lower. Whether these values are close enough is tough to say but I suppose a goodness of fit test could be applied to check for significant departures. The λ values are small because (I think) they represent the probability of observing lilies per m traveled." Fred Schuelerhttps://www.blogger.com/profile/02413290982310369659noreply@blogger.com