Editing Misuse of statistics (section)

===Biased samples===
{{Main|Biased sample}}

Scientists have learned at great cost that gathering good experimental data for statistical analysis is difficult.  Example: The [[placebo]] effect (mind over body) is very powerful.  100% of subjects developed a rash when exposed to an inert substance that was falsely called poison ivy while few developed a rash to a "harmless" object that really was poison ivy.{{sfn|Moore|Notz|2006|p= 97}} Researchers combat this effect by double-blind randomized comparative [[experiment]]s.  Statisticians typically worry more about the validity of the data than the analysis.  This is reflected in a field of study within statistics known as the [[design of experiments]].

Pollsters have learned at great cost that gathering good survey data for statistical analysis is difficult.  The selective effect of cellular telephones on data collection (discussed in the Overgeneralization section) is one potential example; If young people with traditional telephones are not representative, the sample can be biased.  Sample surveys have many pitfalls and require great care in execution.{{sfn|Moore|McCabe|2003|pp=252–254}}  One effort required almost 3,000 telephone calls to get 1,000 answers.  The simple random sample of the population "isn't simple and may not be random."{{sfn|Moore|Notz|2006|p=53, Sample surveys in the real world}}