Statistics

=====Experiments=====
The basic steps of a statistical experiment are:
# Planning the research, including finding the number of replicates of the study, using the following information:  preliminary estimates regarding the size of [[Average treatment effect|treatment effects]], [[alternative hypothesis|alternative hypotheses]], and the estimated [[experimental error|experimental variability]]. Consideration of the selection of experimental subjects and the ethics of research is necessary. Statisticians recommend that experiments compare (at least) one new treatment with a standard treatment or control, to allow an unbiased estimate of the difference in treatment effects.
# [[Design of experiments]], using [[blocking (statistics)|blocking]] to reduce the influence of [[confounding variable]]s, and [[randomized assignment]] of treatments to subjects to allow [[bias of an estimator|unbiased estimates]] of treatment effects and experimental error. At this stage, the experimenters and statisticians write the ''[[protocol (natural sciences)|experimental protocol]]'' that will guide the performance of the experiment and which specifies the'' primary analysis'' of the experimental data.
# Performing the experiment following the [[Protocol (natural sciences)|experimental protocol]] and [[analysis of variance|analyzing the data]] following the experimental protocol.
# Further examining the data set in secondary analyses, to suggest new hypotheses for future study.
# Documenting and presenting the results of the study.

Experiments on human behavior have special concerns. The famous [[Hawthorne study]] examined changes to the working environment at the Hawthorne plant of the [[Western Electric Company]]. The researchers were interested in determining whether increased illumination would increase the productivity of the [[assembly line]] workers. The researchers first measured the productivity in the plant, then modified the illumination in an area of the plant and checked if the changes in illumination affected productivity. It turned out that productivity indeed improved (under the experimental conditions). However, the study is heavily criticized today for errors in experimental procedures, specifically for the lack of a [[control group]] and [[double-blind|blindness]]. The [[Hawthorne effect]] refers to finding that an outcome (in this case, worker productivity) changed due to observation itself. Those in the Hawthorne study became more productive not because the lighting was changed but because they were being observed.<ref name="pmid17608932">{{cite journal |vauthors=McCarney R, Warner J, Iliffe S, van Haselen R, Griffin M, Fisher P |title=The Hawthorne Effect: a randomised, controlled trial |journal=BMC Med Res Methodol |volume=7|pages=30 |year=2007 |pmid=17608932 |pmc=1936999 |doi=10.1186/1471-2288-7-30 |issue=1 |doi-access=free }}</ref>