Tagged Questions

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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Use of Chi2 goodness of fit test with three-level nominal variables from two samples

I have two samples. One is comprised of people who did a pre-test but did not do a post-test (n=75). The other is comprised of people who did both the pre- and post-test (n=150). For each sample, I ...
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8 views

Selecting the right DV in study of treatment effect on a small sample?

I want to run a simple experiment at work to see if making a single change F on a product, has any significant adverse effect on the performance. I need help to ...
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16 views

Some questions about AlgDesign for Fractional Factorial Design in R

I have a few Design of Experiment type questions about the AlgDesign package in R that I can't find answered online: Will using the center=TRUE option in the ...
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35 views

Advice on research study

I am collecting data on extroversion using a personality scale at a clinic. I have about 50 subjects where 15 are in experimental group receiving interventions. I am also collecting data on ...
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1answer
13 views

What is the design of this experiment and what tests are appropriate?

My experiment has the response variable F the experimental unit is a cage the Treatment is rear (1/2 get standard rear & 1/2 get non-standard rear) and there are multiple measures of F over 12 ...
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11 views

Conditions on ratio of $\frac{\sigma_{BIB}^2}{\sigma_{RB}^2}$

I'm attempting to solve a question about the variances of random block design versus balanced incomplete block design. I feel I am close to having an answer, but I'm not quite there yet. Question: ...
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1answer
40 views

Standardized regression coefficients

I have a question regarding standardized regression coefficients and the correlation matrix. I have a two part problem that I am working on, and I need to show that the correlation matrix R is equal ...
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1answer
45 views

What is the correct model for this experiment design?

I have to analyse the results of an experiment, say, a dependent variable Y, in relation to the different treatments applied. However, I am not sure about the model to use with this experimental ...
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1answer
50 views

Minimax space-filling design for 2 dimensions in practice

I think I understand the basic idea of a 2d minimax design. Given $n$ data points, choose locations for each point so that the maximum distance between anywhere in the input space and any of the $n$ ...
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53 views

Show alias coefficient of Plackett Burman design equals $r_{ij}=\frac{c_{1i}'c_{2j}}{N}$

Consider a Plackett Burman design with N rows and let $\beta_{1}$ be the of the regression coefficients corresponding to the main effects and let $\beta_{2}$ be the vector of the regression coefficients ...
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What books to read for Biostatistician position supporting product develpment for in -vitro diagnostics?

This is not a question concerning a specific statistical method, but I need an advice. I am interested in a position as a biostatistician to support product development for in-vitro diagnostics. I ...
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24 views

How to calculate sample size for poll / ranking

Let's suppose there are Y options to choose from. I'd like to run an experiment with a sample of n participants (from a larger population), each will choose 1 option from the Y alternative according ...
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31 views

4-way Repeated Measures ANOVA

exchangers! I am struggling with my data analysis for an article I'm writing. I have to following experimental set-up. Instruction (A/B) Group (Alcohol Dependent / healthy Control) - between ...
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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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20 views

Multilevel propensity score

I'm trying to analyze many treatments on outcome after propensity score 1:1 matching. My problem: I have 6 differents drugs and each patient can take or not each of these. If I build my propensity ...
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1answer
13 views

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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27 views

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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81 views

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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1answer
53 views

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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65 views

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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1answer
16 views

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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8 views

$2^3$ 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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1answer
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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29 views

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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1answer
53 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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0answers
16 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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2answers
27 views

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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1answer
32 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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1answer
26 views

$2^{5-2}$ 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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2answers
30 views

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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1answer
61 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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1answer
23 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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1answer
33 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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1answer
52 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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34 views

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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1answer
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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0answers
113 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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1answer
68 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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1answer
51 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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40 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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2answers
51 views

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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1answer
31 views

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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39 views

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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0answers
14 views

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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1answer
87 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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0answers
17 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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0answers
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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19 views

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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1answer
72 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 ...