While the previous responders have provided some useful advice, it was a bit misleading. The linear model for continuous responses does not automatically assume a normal distribution (of the errors, of which the residuals are an estimate). A specific way of estimating the conditional mean in the linear model assumes a normal distribution of errors. More generally, you can estimate the quantiles of the empirical distribution of the continuous responses with linear quantile regression, which makes no assumption about a parametric form of the error distribution and naturally accommodates heterorgeneity. You can use the median estimate (0.50 quantile regression) as a measure of central tendency rather than the mean. But, almost always it is more informative to estimate some interval of quantiles (say 0.10 to 0.90) to adequately characterize how the response changes with covariates. More advanced transformation approaches with quantile regression will allow you to handle proportions (responses bounded on [0, 1] interval) and discrete counts.
Brian Brian S. Cade, PhD U. S. Geological Survey Fort Collins Science Center 2150 Centre Ave., Bldg. C Fort Collins, CO 80526-8818 email: ca...@usgs.gov <brian_c...@usgs.gov> tel: 970 226-9326 On Thu, Aug 8, 2019 at 5:16 AM Chitra Baniya <cbban...@gmail.com> wrote: > We have the data of "gall_diameter" and "elevations". Our objective is to > see how does gall diameter vary along the elevation gradient. In our case > the elevation gradient refers to the range between 1500 to 2500 m asl with > data collected in every 250 m interval. > Our data did not follow normal distribution. Gall_diameter is a continuous > dependent variable. Can we apply "glm" to see the relationship between > gall-diameter and elevation in our case? > How can we decide the distribution in our data and its family? > Thank you all in advance for your help. > > > -- > > > > > > > *Chitra Bahadur Baniya, M Sc, M Phil, PhDAssociate ProfessorCentral > Department of BotanyTribhuvan UniversityKirtipurKathmandu, Nepal* > orcid.org/0000-0002-8746-7601 > > [[alternative HTML version deleted]] > > _______________________________________________ > R-sig-ecology mailing list > R-sig-ecology@r-project.org > https://stat.ethz.ch/mailman/listinfo/r-sig-ecology > [[alternative HTML version deleted]] _______________________________________________ R-sig-ecology mailing list R-sig-ecology@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-ecology
