Experimental design, or design of experiments (DOE), is the design of any information-gathering exercises where variation is present. In statistics, controlled experiments are usually implied, which involve an "experimental group" and a "control group". In the design of experiments, the ...

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Selecting control locations for tiered groups?

I have groups of locations categorized by their sales performance and weekly variability into four tiers. We are running on-site tests for 100 locations in Tier A against a set of 50 control locations ...
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Moderated regression in repeated measures

I recently conducted a study with 4 within-subject conditions, divided over two sessions. My independent variable is degree of emotional eating (as measured by food intake after a negative mood ...
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Sample size and power calculation

I am looking for an advice on sample size and power calculation for an intervention study. The study uses a stepped wedged design. The study aims to evaluate the effectiveness of case managers ...
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Model selection using an artificially insignificant covariate

This is continued from my other post on model selection. Let me provide more details first. 1) I have a factorial design. Factor A has 5 levels, B has 2 levels, C has 2 levels. Let us assume that ...
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Is Hurlbert 1984 the best introductory overview to pseudoreplication?

I often find myself explaining (or wanting to explain but not wanting to be boorish) the basics of random sampling and the consequences of pseudoreplication, specifically the limitations and ...
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Stratified or multi-stage sampling?

I just started volunteering with a small organization that wants to estimate the average and total number environmental trouble spots in a large US city. They have a clear definition of an ...
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Augmenting PB Design to Full Factorial

I’m planning to augment PB design to full factorial. But not able to understand statistically am I correct or not? Let me explain with example. Initially I had 11 factors & conduct PB using 12 ...
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$2^3$ Factorial Design conducted in a Latin Square Design

When does the situation occur to conduct a $2^3$ Factorial Design in a Latin Square Design? What would be the procedure of analyzing data of a $2^3$ Factorial Design conducted in a Latin Square ...
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56 views

Design of Experiments

Suppose a dermatologist wants to study the effectiveness of two different preparations of a skin lotion using two different forms of application, such as one versus two applications per day. She has ...
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A full-factorial experiment showed an interaction is significant - how do I use that?

I ran an experiment with a full factorial design. It showed that Factors A and B and the interaction ...
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38 views

Random and Fixed effect model

Would you explain a practical situation where random effect model is more appropriate than the fixed effect model?
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Data capture in psychological treatments - nonmandatory random repeat questions

this is a query for approaching a prospective exploratory study in psychological treatments It is not very easy to monitor response to psychological interventions. Usually there are standardized ...
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14 views

Fractional Factorial Design with Highest Resolution

In the book Design and Analysis of Experiments by Douglas C. Montgomery , it is written that We usually like to employ fractional designs that have the ...
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How to select a control / comparison group?

Lets say I'm creating a study that looked at treatments for metastasis in African American colon cancer patients. Would my control group or comparison group be Caucasian colon cancer patients with ...
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30 views

Fractional Factorial Design

In a $2^5$ design, it is believed that only the main effects $(A,B,C,D, E)$ and $AB,AC$ interaction effects are non-zero. I need to construct a fractional factorial with minimum number of runs which ...
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$2^{5-2}$ Design : Alias Structure

$2^{5-2}$ Design Design Generators: $D=AB\quad E=AC$ Defining Relation: $I=ABD=ACE=BCDE$ $$\text{Aliases}$$ $$A=BD=CE=ABDE$$ $$B=AD=ABCE=CDE$$ $$C=ABCD=AE=BDE$$ $$D=AB=ACDE=BCE$$ ...
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How should I design an experiment with non-binary factors?

We are preparing an experiment that will run during the coming winter, where we assess certain energy performance indicators on a set of single-family houses in Europe. We are interested in finding ...
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60 views

Why people often optimize the determinant of $(X'\Sigma X)^{-1}$

Say I have a random vector $Y\sim N(X\beta,\Sigma)$ and $\Sigma\neq\sigma^2 I$. That is, the elements of $Y$ (given $X\beta$) are correlated. The natural estimator of $\beta$ is ...
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21 views

Experimental design considerations for Randomized Block design

Is there a use of using a Randomized Block design when you only have one treatment and you only want to test the effects of this single treatment? The experiment in question is to see whether a ...
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26 views

Extremely new to R: Support.CEs package - help with design matrix please!

I've only started using R one day ago, still so much to get my head around. I need to create a choice experiment, and I have been following the example of H.Aizaki I think I have created a successful ...
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48 views

Random Effect Model

One factor random effect model: $$y_{ij}=\mu+\tau_{i}+\epsilon_{ij}\quad i=1,2,\ldots,a; j=1,2,\ldots,n$$ where, $y_{ij}$ is the $j$th observation of $i$th treatment effect $\mu$ is the overall ...
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Computing the F-ratio under null hypothesis

Statistical model for a Completely Randomized Design: $$y_{ij}=\mu+\tau_{i}+\epsilon_{ij}\quad i=1,2,\ldots,a; j=1,2,\ldots,n$$ where, $y_{ij}$ is the $j$th observation of $i$th treatment effect ...
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36 views

Which design is most appropriate?

I have data from an experiment testing a new treatment. Each subject has 4 data points, 2 of the new treatment and 2 of the control. It is like a paired analysis, but instead having 1 observation of ...
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77 views

logistic regression with dummy variables for fractional factorial design

We have conducted a survey experiment with varying amounts of incentive (factor 1 = I1, I2, I3, I4, I5). The experiment was conducted stepwise in three subsequent studies (factor 2 = S1, S2, S3). ...
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65 views

Is there an equivalent to LHS for a discrete input space?

I was wondering if there is a method that is equivalent to Latin Hypercube Sampling when the input space you are trying to sample from are a finite discrete set of possible values. For example, if I ...
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47 views

Identifying the experimental unit

I have included a diagram of an experiment where cells are pooled from multiple animals, cells from the pool are then allocated to different treatments and a measurement is taken from each individual ...
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34 views

Correct use of Mixed model for random block design?

I have the following experimental design (random block design). Block with 4 Treatments (A, B, C, D) repeated at 4 different sites. Treatments were applied to individuals of different species (factor ...
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How to analyze this messy design?

I need to analyze a data-set, with a very messy design, I am not sure how. I will try to make it simple. A new kind of stitches was invented, and is tested vs. 2 old kind of stitches. I will call ...
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Multiple measurements of a single datapoint: what to do with variability?

I am interested in a general question about research design, but I will explain it on a specific example. Suppose I want to determine if one group of people has higher heart rate than the other ...
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Threshold for psychometric experiment with three (or more) possible choices

I'm running an experiment where subjects are viewing a stimulus, and they have to decide if the stimulus is brighter/darker/identical in respect to a standard image. Stimulus luminosity actually ...
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Logistic Regression and Design of experiment

I have seven factor and one response variable with 32 run and one replication i.e. 64 runs and I want to use logistics regression. I found in th analysis that 4 out 7 factors are significant. I want ...
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66 views

How to create a nearly orthogonal experimental design in R?

Does anyone know an R package for nearly orthogonal designs? I would like to create an experimental design, using 12 runs, up to 10 factors, and with mixed levels (e.g. a combination of 2 and 3 level ...
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15 views

counfounded batch effects in microarray dataset - can I do partial experiment redesign?

I'm working with a microarray data set where the batches are completely confounded treatment time, i.e. time t1 is all in batches b1 and b2, and time t2 is all in batches b3, b4, and b5. I know this ...
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8 views

Choice of dependent variable: Differencing or Controlling?

I was running some analysis where I suspect that a treatment $D$, has opposite effects on two variables $Y^A$ and $Y^B$. To show that, I was thinking about two strategies: 1. Differencing Running ...
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What are the statistical implications of assigning treatment and control in time series study under 2 different approaches?

I have a project wherein my group wants to measure the effect of counseling at-risk students on their academic outcomes. There are 1,000 students who will be enrolled during the current academic ...
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56 views

Experimental design and mixed models

I want to test effect of 3 PH on larval development. I would like to know what is the best experimental design and statistical analysis. We can only use 3 compartments of sea water, each one with a ...
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Sample size calculation for multilevel, longitudinal experiment

I'd be grateful for any advice about how to do a sample size calculation for the following design. We are interested in the impact of two variations of an intervention on hospital in-patients' ...
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35 views

Controled Factorial Experiment Design: which name or resource?

I'm designing an experiment which has to factors (A,B) with respectively 4 and 5 levels. Since this is quite a large amount, I figured I use a factorial design. However, it is unclear whether the ...
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Is it OK to take “Analysis of Variance in Experimental Design Models” Before a Regression Course?

I am a math major starting a MS program in statistics. I have taken an undergraduate sequence in stats (basics of distributions, estimation, hypothesis testing) but never a formal course in ...
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How do I define generators in Minitab

How do I define generators in Minitab 16? I have an experiment design (DOE) with 5 factors and 2 generators. I entered D=ABC E=AC in the box of generators but it says only F through G ?
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39 views

Can I hypothesise an insignificant mediation? (Very basic stats)

This is for a simple psychology report. I was wondering if I could hypothesise an insignificant mediation. Eg: "...based on this research it is predicted that group identity is not a significant ...
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38 views

Establishing significance levels post-hoc

Proper frequentist procedure says that we should establish a sampling plan, statistical analysis and significance level before we start an experiment. We then report whether or not we reject H0 for ...
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Interpreting covariates in 2 by 2 MANCOVA

I am doing 2 by 2 MANCOVA with experimental data set. Followings are variables I used. DV1, DV2, IV1, IV2, and C1 where DV=dependent variable, IV=independent variable, and C=covariate. Consistent ...
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107 views

What type of Research Design?

In an experiment, 25 subjects (Group A) are assigned to play an adventure game (with audio and non-audio) while another 25 subjects (Group B) are assigned to play a strategy game (with audio and ...
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Difference between Research Design and Experimental Design

What is the difference between Research Design and Experimental Design? I can't see any difference. Both of them need to establish Causality. Both of them are the arrangement for collection and ...
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Type-1 Error of the Two-Stage Design

Background on Two-Stage Designs In clinical trials, we are often interested in the response rate $p$ for an experimental treatment. In a typical trial, we might expose $n$ patients to the treatment ...
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How to deal with outlier in the experiment

My question is related to this one. I'm working on an experiment involving transferring data between different locations all over the world via the Internet. As the Internet can be busy, sometimes it ...
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What's the sample size required to confirm that two treatments are identical?

Goal: Determine if a machine is defective Say I am going to give the same treatment to a group of people. I have a machine that will randomly split them into $2$ groups before giving the same ...
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Augmented split plot experimental design

I planned a field experiment with different genotypes according to an augmented design (check repeated entries plus unrepeated entries). Since I am testing a segregating population, each plot split ...
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What is the meaning of $A(B^2)$ interaction in a 3 level factorial with 2 factors $A$ and $B$, when the factors are qualitative?

I understand that when the factor is quantitative the $AB$ interaction can have a linear component and a quadratic component and so $AB^2$ makes sense there. But when we have qualitative elements how ...