Design of Experiments


September 11, 2012 | Wesley

One-Way ANOVA Analysis of variance is a tool used for a variety of purposes. Applications range from a common one-way ANOVA, to experimental blocking, to more complex nested designs. This first ANOVA example provides the necessary tools to analyze data using this technique. This example will show a basic one-way ... [Read more...]

Fractional Factorial Designs using FrF2

May 18, 2011 | Ralph

The FrF2 package for R can be used to create regular and non-regular Fractional Factorial 2-level designs. It is reasonably straightforward to use. First step is to install the package then make it available for use in the current session: require(FrF2) A basic call to the main functino FrF2 ... [Read more...]

Generating Balanced Incomplete Block Designs (BIBD)

July 16, 2010 | Ralph

The Balanced Incomplete Block Design (BIBD) is a well studied experimental design that has various desirable features from a statistical perspective. The crossdes package in R provides a way to generate a block design for some given parameters and test wheter this design satisfies the BIBD conditions. For a BIBD ... [Read more...]

Design of Experiments – Block Designs

February 20, 2010 | Ralph

In many experiments where the investigator is comparing a set of treatments there is the possibility of one or more sources of variability in the experimental measurements that can be accounted for during the design stage of the experimentation. For example we might be investigating four different pieces of machinery ... [Read more...]

Two-way Analysis of Variance (ANOVA)

February 15, 2010 | Ralph

The analysis of variance (ANOVA) model can be extended from making a comparison between multiple groups to take into account additional factors in an experiment. The simplest extension is from one-way to two-way ANOVA where a second factor is included in the model as well as a potential interaction between ...
[Read more...]

One-way ANOVA (cont.)

February 12, 2010 | Ralph

In a previous post we considered using R to fit one-way ANOVA models to data. In this post we consider a few additional ways that we can look at the analysis. In the analysis we made use of the linear model function lm and the analysis could be conducted using ...
[Read more...]

One-way Analysis of Variance (ANOVA)

February 3, 2010 | Ralph

Analysis of Variance (ANOVA) is a commonly used statistical technique for investigating data by comparing the means of subsets of the data. The base case is the one-way ANOVA which is an extension of two-sample t test for independent groups covering situations where there are more than two groups being ...
[Read more...]

Design of Experiments – Full Factorial Designs

December 1, 2009 | Ralph

In designs where there are multiple factors, all with a discrete group of level settings, the full enumeration of all combinations of factor levels is referred to as a full factorial design. As the number of factors increases, potentially along with the settings for the factors, the total number of ... [Read more...]

Design of Experiments – Optimal Designs

November 29, 2009 | Ralph

When designing an experiment it is not always possible to generate a regular, balanced design such as a full or fractional factorial design plan. There are usually restrictions of the total number of experiments that can be undertaken or constraints on the factor settings both individually or in combination with ... [Read more...]

Design of Experiments – Power Calculations

November 18, 2009 | Ralph

Prior to conducting an experiment researchers will often undertake power calculations to determine the sample size required in their work to detect a meaningful scientific effect with sufficient power. In R there are functions to calculate either a minimum sample size for a specific power for a test or the ... [Read more...]

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