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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Multiple pairwise comparison DOE

I'm going to conduct experiment with 7 products. One subject can evaluate no more than 3 products. The ultimate goal is to compare all 7 products to each other (let say, on means) and rank them. So, ...
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Interpretion of ANOVA with Nested Design

The following scenario is a basic nested design. I am trying to wrap my head around the interpretation of the ANOVA Table. Scenario: A school administrator is looking to investigate 5th grade ...
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Design of experiment - coding, method to analyze data

We have data from an experiment where there are two groups. They are both measured at time 0, before training and one of the group is trained the other is not. We measure some outcome variables ...
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21 views

Random Effect Model and Response Surface Methodology

In Design and analysis of experiment , Random effect is defined as : An experimenter is frequently interested in a factor that has a large number of possible levels. If the experimenters randomly ...
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34 views

Number of trials necessary to demonstrate Bernoulli process doesn't have mean p

I have a Bernoulli process that purportedly has mean $x$ but I hypothesize that the process actually has mean $q$. How many trials are necessary to demonstrate (to some confidence $p$) that the actual ...
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33 views

What kind of research design is this, is it even possible? If so, how to go about analyzing it?

This is for a psychology design. I have 2 groups, all members of both groups are to be administered all tests. I think that I want to do a 3x2 factorial ANOVA on the DIFFERENCES in the means of my ...
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29 views

Statistical Significance , which approach?

[editing original post to clarify my question] I have looked at some of the other posts on this but still can't grasp if these 2 are different approaches to determining somethings stat sig, or if ...
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16 views

Other options for a 2x2x2 RCT design that would require less participants

Alright, imagine the following: I would like to assess (the main effect & interplay of) three independent variables (i.e. A, B, and C) on a dependent variable Y. In addition, each independent ...
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21 views

Research Design Question

We have collected data from one group of students (post-only) where students went through two versions of online discussions (large group vs. small group) and then rated their overall experience in ...
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38 views

How to deal with subjects who cannot receive the treatment in an experiment?

Imagine an experiment where you are trying to establish that cell phone users who receive a a local offer tend to spend more. How do you deal with those in the test group that cannot receive the ...
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24 views

Different groups, same intervention. What design is this?

I'm trying to figure out the best way to analyse the following clinical trial: Group1: Healthy individuals Group2: Diseased individuals Both groups follow the same intervention and are tested pre- ...
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Matching two populations that have different disease status that have undergone the same intervention?

If there are two populations, D+ and D-, where D is disease state, and both populations have undergone an intervention I, what would be the best way to design that study? Given that this is ...
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39 views

Help with analyzing/planning a physical experiment — regression

This is a real experiment about to be performed Batches of samples will be prepared. A Striker will be used to see if a reaction will occur. For example: 20 drops might be performed, and number of ...
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123 views

Mixed-effect model design with a sampling variable

I am trying to specify a formula for a linear mixed effect model (with lme4) for my experimental design, but I'm not sure I'm doing it right. The design: basically ...
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51 views

Comparing distributions from a factorial design

I have the following experimental design: I have six animals, where three received treatment and the other three were used as control (so treatment and control animals are not paired). From each of ...
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58 views

Size of Tukey's 1 Degree of Freedom Test

In Oehlert (p. 218) the following algorithm for computing Tukey's one degree of freedom test for non-additivity is suggested: Fit a preliminary model; this will usually be an additive model. ...
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If I have a 2x2 table of proportions of treatment effects, what is the best test to use for treatment effect?

I currently have a 2x2 table of proportions for treatment effects that looks like: \begin{table}[h] \begin{tabular}{lll} & Treatment A & Without Treatment A \\ Treatment B ...
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26 views

Cyclic Block Design with multivariate adaptive regression splines

I came upon a question of a linear block design for reviewing an article. The experimental design looked as follows: Material of different compostion (9 different combinations) was incubated in a ...
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24 views

Why would one not stratify random assignments in a controlled trial?

With some frequency I read reports of randomized controlled trials where, despite the randomization, a baseline survey found significant between-group differences in important covariates. It seems to ...
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How to determine number of replicate in DOE mathematically?

Actually, almost all of agriculturist define the number of replicate in their design of experimentally is based on subjective approach like experience, field condition, and so on. Even we know that ...
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31 views

Strange two sample z test result in experiment

I performed an experiment on a virtual population wanting to see whether Vitamin C can positively affect performance on an IQ test. I gathered 80 people and grouped them into two groups of 40. ...
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Biology IRP Design Help

So for my biology final I need to design and test an experiment. The idea was to test for a significant difference in the cleanliness of my library's 2 computer stations (8 computers each) and quick ...
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120 views

How to prevent collinearity?

Ieno & Zuur 2015 describe a number of causes of collinearity among explanatory variables entered into a linear regression. One of these causes is what they call a 'data collection' cause. They ...
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62 views

Identification problems with a structural equation model of experimental data

I have performed an experiment in which I manipulated three factors and I would like to model latent variables that those factors affect and then estimate the effects of the latents on response ...
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29 views

Augmenting experiment design matrices

Consider a set of users (rows) where we are already testing several treatments (columns): $$\begin{pmatrix} E & U & E \\ U & E &E \\ \vdots & \vdots &\vdots \\ E & E ...
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Within Subjects Design question

I have 75 participants and each participant has an exam on 15 questions. These questions are words. Their answers are 0 and 1 (knownn-unknown). Then I have another variable, their fixation on those ...
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Can I use experimental data from one experiment in another?

I ran an experiment with a simple 2 x 2 factorial design. Subjects were high school students. Factor 1 = school (school 1, school 2). Factor 2 = group (treatment/control). N = 322, split quite ...
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32 views

When would you use an I-optimal design over a D-optimal design?

We were discussing in DOE designs that it was best for model development to us d-optimal designs to identify your design space. The common alternative would be an i-optimal design. When would it be ...
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79 views

How can I measure difference between non-parametric data with many zeros?

I'm comparing two groups of students by their course activity and I'm struggling a little to determine the best way to test for significant difference. The data is non-normal, and very prevalent with ...
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17 views

How do I calculate the sample size required for a crossover AB|BA study?

I would like to know whether it is feasible to conduct this study. We have a subset of people in facility A (n=1300 per year), of which a proportion of these present a condition (n=18). Similarly, we ...
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111 views

Misfitting of drift rate in Wiener model

In a binary-decision experiment, the accuracy and response time of some subjects were recorded. My goal is to fit a Wiener model to response time and accuracy data. The binary experiment has three ...
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58 views

Advantages of counterbalancing vs. randomizing stimuli

I'm designing an experiment, in which 40 participants answer 10 questions, 5 in condition $A$ and 5 in condition $B$, and I'm interested in the difference between the two conditions. It's not clear ...
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27 views

Clustering MVT response data by audience

We are doing multivariate testing 4 possible values for each of 3 variables on a landing page: (a) offer presented, (b) product claim message displayed and (c) image used. So, 12 dummy variables, 64 ...
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6 views

Response surface models using quantitative variables

This relates to the mineral industry so a little context first. We are trying to estimate the uncertainty in the amount of ore that can be recovered from an ore body mine. This depends on things ...
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Multiway anova doubts

I am new to statistical inference. I have read about one-way/multi-way anova and also between subjects and within subjects design. I would like to conduct a subjective quality test and analyze the ...
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42 views

what should be the null hypothesis?

conduct a test hypothesis to show that it takes longer for people with average fitness to successfully complete physical therapy as compared to those with above average physical fitness. Test at ...
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How can I prove the variance of residuals for an unbalanced one-way layout?

How can I prove the variance of residuals for an unbalanced one-way layout? var($e_{ij}$)=$σ^2$($1- \frac{1}{n_i})$ here i = 1,...., a j = 1,....$n_i$ where $e_{ij}$'s are the residuals. where ...
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49 views

What wrong with this experiment methodology?

The following experiment was devised: a group (random) was divided randomly into 2 : Half were give coffee A the others coffee B, all rated it on a 1-5 Likert scale. Results where analyzed using ...
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26 views

experimental longitudinal design?

Is a longitudinal study really by definition/always correlational? How about a repeated-measures experiment: I would've called that an experimental longitudinal design. (For example, you randomly ...
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31 views

Why do contrasts or contrast sum of squares have one degree of freedom?

I have repeatedly seen that contrasts or contrast sum of squares are mentioned to have one degree of freedom. I'm wondering why this is the case. Is there an obvious explanation? Shouldn't they have ...
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57 views

How to interpret D-Efficiency in Experimental Design?

I created an orthogonal design in R using AlgDesign package. I got 14 profiles and some output: D =0.2519353; A = 5.462121; Ge = 0.748; Dea = 0.714. How to interpret D , A , Ge and Dea? Also, In ...
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20 views

ANOVA table for alpha latice design?

I have my trail in alpha lattice design with three replications, 32 blocks in each replication, 10 plots per block, and with 320 treatment, please suggest to me an ANOVA model for this analysis.
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Difference between “Design based approach” and “Model based approach”?

In a pdf file, i found the following thing which i have not understood at all. ‐ one view (e.g., Heckman, 2008): causality is model‐based: causality only exists within the framework of a theory ...
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31 views

Study design: equal/unequal sample sizes

I have recently sent a paper on aflatoxin levels in nuts for publishing. The aim of the study was to analyze a total amount of 106 nuts. The nuts were divided into four categories: walnuts (n=33), ...
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31 views

Adaptive Sampling Design

In a pdf, the definition of adaptive sampling design is written as : "An adaptive sampling design is one in which the selection of units to include in the sample depends on ...
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63 views

Do the different levels of treatment in a completely randomized design come from different population?

Suppose in a completely randomized design , a treatment A have four levels. When we check whether the means of four levels are statistically significant ,i.e., $$H_0:\mu_1=\mu_2=\mu_3=\mu_4$$ ...
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multiple repeated within subjects pre test measurements in fully crossed design

Which statistical test should I use if my design has a baseline pre test for 3 treatments? Each subject gets all 3 treatments each on different days. Each day has a pre treatment baseline measure. ...
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18 views

Randomization for multi-site clinical trial, screen failures

Two questions about appropriate randomization procedures for a small two-armed trial at 3 sites. About 100 participants total, evenly split between study arms. First, we are concurrently enrolling ...
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Should I use baseline condition when comparing two “treatment” conditions?

I'm interested in comparing performance (measured in proportion of correct trials) on a visual perception task between two "difficult" conditions. Normally, I'm interested in measuring performance ...
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Is it valid to use a generalized model with no replicates

I've got a designed experiment that is a long-term agricultural station. The field is divided into 11 rows and 6 columns (each column has two sub-columns). Each resulting plot represents a unique ...