Consider again an experiment that seeks to determine the causal relationships between factors and the response, where . Ideally, the sample size is large enough for a full factorial design to be used. However, if the sample size is small and the number of possible treatments is large, then a fractional factorial design can be used instead. Such a […]
Having taught and tutored introductory statistics numerous times, I often hear students misinterpret the Central Limit Theorem by saying that, as the sample size gets bigger, the distribution of the data approaches a normal distribution. This is not true. If your data come from a non-normal distribution, their distribution stays the same regardless of the […]
To summarize what we have learned about experimental design in the past few Applied Statistics Lessons of the Day, let’s use an example from physical chemistry to illustrate these basic principles. Ammonia (NH3) is widely used as a fertilizer in industry. It is commonly synthesized by the Haber process, which involves a reaction between hydrogen […]
The goal of an experiment is to determine whether or not there is a cause-and-effect relationship between the factor and the response the strength of the causal relationship, should such a relationship exist. To answer these questions, the response variable is measured in both the control group and the experimental group. If there is a […]
We have written a bit on sample size for common events, we have written about rare events, and we have written about frequentist significance testing. We would like to specialize our sample size analysis to rare events (which allows us to derive a somewhat tighter estimate). In web marketing and a lot of other applications […] Related posts: Estimating rates from a single occurrence of a rare event A bit…
The failure of mainstream research to consistently reproduce results have led many to look for the faults in current methodologies.One of these potential faults identified is that the significance levels of current standards is too high. A standa...
In our article What is a large enough random sample? we pointed out that if you wanted to measure a proportion to an accuracy “a” with chance of being wrong of “d” then a idea was to guarantee you had a sample size of at least: This is the central question in designing opinion polls […] Related posts: What is a large enough random sample? Level fit summaries can be…
