title: Citizen science: best practices to remove observer bias in trend analysis.
abstract: Citizen science, time series records over long periods of time, and wide geographic areas offer many opportunities for scientists to answer questions that would otherwise be impractical to investigate. Citizen scientists currently play active roles in a wide range of ecological projects; however, observer biases such as varying perception of events or objects being observed and quality of observations present challenges to successfully derive interannual variability and trend statistics from time series records. It is recommended that citizen science records, particularly those involving events such as plant phenology, should not be directly averaged across sites. The interannual variability expressed as an anomaly and trend expressed as a regression slope should be calculated for each site. Only the site level anomaly and regression slopes should be averaged to suppress observer biases.
authors.affiliation: Department of Geography and Program in Planning, University of Toronto, Ontario, M5S 3G3, Canada, gonsamoa@geog.utoronto.ca.
authors.forename: Alemu
authors.initials: A
authors.lastname: Gonsamo
authors.forename: Petra
authors.initials: P
authors.lastname: D'Odorico
mesh_terms: D003256:Community Participation; D003625:Data Collection / Q000706:statistics & numerical data*; D006801:Humans; D019684:Magnoliopsida / Q000254:growth & development*; D015588:Observer Variation; D018515:Plant Leaves / Q000254:growth & development*; D012106:Research / Q000706:statistics & numerical data*