Questions tagged [blocking]

In the design of experiments, blocking refers to grouping similar experimental units together in groups ("blocks"). Comparing treatments based on within-block differences reduces the influence of extraneous variables, thus increasing power.

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44 views

Do I want a mixed model for fractional factorial designs?

I have created a d-efficient fractional factorial design of 48 combinations from a total of 192 possible combinations (4x2x2x3x2x2). For the experiment, I plan to have 4 runs in 12 blocks and 40 ...
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335 views

Balanced incomplete block design

In a BIBD, let $a$ denote the number of treatments; $b$ denote the number of blocks; $k$ denote the number of treatments exactly in each block; $\lambda$ is the number of times each pair of ...
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What is the meaning of “each treatment ” in BIBD?

(I am restating the question again in a more clear manner, as it was not clearly written last time) My doubt is regarding Balanced Incomplete Block Design (BIBD) Consider the following design with ...
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which experimental design better fits?

I test the effect of a plant dose on the abundance of a specific microbe, cultured in glass tube in vitro. The treatment consist of 5 doses (0, 1, 2, 3, 4). Each culture tube receives one of the dose ...
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Blocking vs. Control

Am I thinking about this correctly? Blocking is something that is done on the experimental design level: If I'm not interested in the differences between school districts, I block by school district ...
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appropriate error term for a randomized complete block design, possible split plot in time, with subsamples (in SAS PROC MIXED))

I am analyzing the results of an agricultural experiment, as follows: Plots are laid out in a randomized complete block design with 3 reps. They have been either conventionally or organically managed ...
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38 views

Why is ABC interaction completely confounded in this factorial experiment?

Consider a 2^3 factorial design layed out in 2 blocks ,with plot size 4, as follows Block I: {1,ab,ac,bc} Block II: {a,b,c,abc} This is replicated four times. abc is said to be completely ...
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79 views

mix model for averages or for raw data

I have classic block design of the experiment. There are blocks and treatments, and several observation within. The experiment is unbalanced thus I want to use mix models to analyze if the treatment ...
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224 views

Is this a Blocked design ANOVA, two way anova, or ANCOVA

I am running ANOVA to test for a significant effect for some data, and a grad student said I should run an ANOVA test formatted like this in R to test for significance: ...
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Identifying treatments with non-zero effects

I have a complete block design experiment with a large number of treatments were I am trying to identify treatments with significant effects (positive or negative). I know the Friedman/Durbin tests ...
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500 views

Examples of connected designs in DOE

I want to understand connectedness in block designs , I know this about connectedness : a design is said to be disconnected if we are able to create two separate groups such that they do not contain ...
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Crew selection: ranking rowers by letting them race against each other

Seat selection is a common practice in competitive rowing and I would be curious about more solid statistical underpinnings: there are more rowers in a team than the 8 seats in the crew boat. So the ...
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Randomized Block Design Models

I have been asked to fit the following models in R: The models are based on this data: I know the mediums are the blocks and the units of the active ingredient are the treatments. I understand how ...
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69 views

Incomplete block design analysis

I have 4 treatments (6m, 12m, 24m, 40m) in 3 blocks, but all treatments are not replicated in these blocks: 6m, 12m, 24m are in Blk1 and Blk2 and Blk3 consist of only 34m (control plot) and 6m. How ...
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Paired $t$-test with multiple values

With the following data, I believe the difference in performance between two athletes can be measured with a (one- or two-sided) paired $t$-test: ...
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When to use blocks?

I am currently studying Random Complete Block Designs (RCBD) and I would like to ask a question. I cam across an example where we were able to conclude with the RCBD as significant, but regular ANOVA ...
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Test for yield and disease incidence in block design

I need to analyse a set of data coming from an agricultural experiment, with the intention of assessing the incidence of a certain disease in potatoes under three different treatments (plus blank). I'...
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Random block design ANOVA in R

Quick question: I have found this tutorial which recommends a two-factorial design for the following setup: three menu items (fixed factor) are tested in six restaurants (random factor). The guide ...
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In marketing experiment, can we determine the effect customer state has on response?

We have the goal of determining whether an email campaign has an impact on the amount of product that customers purchase. We have customers from several states but much more from some states than ...
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defining arbitrary blocks

In an experiment with 4 treatments (a, b, c, d) and 3 observation per treatment, is it valid or desirable to impose $n$ blocks on the design. That is there is nothing that distinguishes the blocks. ...
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How Is This Design a Randomized Complete Block Design?

I recently started learning about one-way ANOVA, multiple comparisons, and contrasts. At the moment, I have an introductory-level knowledge of these concepts. I'm analysing an experiment that ...
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Randomized blocking “after the fact”

I have 5 treatments that I'm going to randomly assign to visitors to my website. I'll have 10,000 or more visitors. Is it statistically valid to analyze the results based on visitor characteristics ...
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108 views

Specifying ANOVA with incomplete block design (R)

I have experimental data of individual sizes (continuous) as a function of two categorical variables (A and B) each with 2 levels (1 and 2), along with a control treatment. Each treatment condition ...
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1answer
28 views

Restricting block size in a factorial experiment

I have the following: It has been decided to run an experiment involving 2 replicates of a $2^4$ factorial with factors coded A, B, C & D. However, block size is restricted to 8 I'm not sure ...
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standardising independent and dependent variables within blocks?

I have data from a randomised blocked experiment testing the effect of different crops on weeds. Each treatment was replicated in one plot in each of three blocks, on two farms, in two years (but NOT ...
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What makes a block a block

In multivariate analysis involve analysing different data sets of the same individuals, sometimes it is called integration or multi-block analysis. However I can't find how are these dataset defined: ...
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Blocking effect in Experiment

Let $T\in\{0,1\}$ be the variable representing the treatment. Let $X\in\{0,1\}$ be the variable representing the attributes of subject. For example, $T$ is a new medicine that will make people grow ...
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Balanced Incomplete Block Design (BIBD)

If treatment $1$ appears in $r$ blocks and there are $(k-1)$ other treatments in each of those blocks, there are $r(k-1)$ observations in a block containing treatment $1$. But the following Table ...
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Coefficients in a Randomized Block Design

If, for example, I am running a GLM with Poisson distribution (it could be any distribution) and I have a Randomized Block Design (RBD) [Note: I dont wanna run a GLMM just to put the blocks as a ...
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What statistical test would be best for before and after comparisons of multiple similar groups?

I can't exactly give the problem I'm working on but I will give a sensible example of how it looks: I have 4 groups of people: diabetes, depression, schizophrenia, dementia, notice how a person with ...
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50 views

What statistical test should I use to compare before and after drug treatment in a group of 8 subjects?

I have a group of 8 subjects. For each subject I measure their heart rate 30,20, and 10 min before and after they take a drug. I then average the heart rate measurements in each subject to get one ...
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84 views

Best way to do block randomisation with covariates?

I have a set of $n$ objects for an experiment and I want to randomise them into a control group and treatment group with fixed sizes. I would like to use block randomisation to balance covariates, in ...
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How to generate a Randomized Complete Block Design?

I'm studying agriculture and I'm looking for answers concerning one of my problem. I have to implement a randomized complete block design and I would like to generate it with R. I've found some ...
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Can covariates be categorial variables?

I have a 2x2 experimental design. In the experiment, I also collected the participants' professional qualifications (categorical variable- yes /no). I would like to test the effect of controlling this ...
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108 views

Random block mixed ANOVA

We tested proliferation of 4 types of cells (between-subject factor) during 3 consequent time points (within-subject factor). All test were done in 4 blocks with 1 plate of each type of cells in each ...
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704 views

Applying a mixed effect model on autocorrelated nested data?

I’m having a hard time figuring out what type of model I should use to analyse data with a rather complexe design. Experimental goal and protocol: The goal is to study the effect of beehive color ...
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93 views

SAS code to check normality assumption of random effect on blocks in a RCBD

I have a model with 2 factors of treatment and a block effect that the block is a random effect. for checking the assumption I need to check the normality, equality and independency of the variance of ...
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adonis in vegan: order of variables or use of strata

I am using the adonis() function in in the vegan package to determine 1) if co-occurring host species vary in their microbial ...
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1answer
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Is there an experimental design that tests three different factors?

I am planning on performing data collection on subjects to see how well certain wearable products perform. Let's call the products A, B, and C. The goal is to see if any of the products performs more ...
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Is there a generalisation of Wilcoxcon paired sign-rank test to compare more than two connected samples?

I have a table where columns denote customer, row-supplier, cell- total amount of items, sold by supplier to customer. I have a zero hypothesis(H0) about random choise of customers and H1 hypothesis(...
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495 views

Sum of Squares in Randomized Complete Block design

I'm interested in the Randomized Complete Block design (RCB) with three treatments, which I call $A$, $B$, and $C$, and four blocks ($b=4$): \begin{align} \textrm{block 1: } (y_{A,1}; y_{C,1}; y_{B,...
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Difference between one-way ANOVA with randomised blocks and nested ANOVA?

I'm doing a biology course and am very inexperienced with stats. My supervisor recommended that I go away and try an ANOVA with block design, but I hadn't heard of this. Having looked up about it, I ...
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292 views

Is resampling more accurate than block average for statistical analysis of data (cross-post)?

this is a cross question I asked on the computer science community before I was advised to cross-post it here. I'm working in laboratories where molecular dynamics data are almost always analysed ...
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Comparing two metrics from the same plot. Should I use a two-way ANOVA?

I have the following design. In each sampling plot, I measure food in four patches (BD, BF, OD, OF). From those I calculated preference for B trays and for D trays. So for every sampling plot I have ...
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1answer
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Incomplete block design analysis / design with R

I have a few questions that arose when working on designing the following experiment. The numbers and variable levels are all made up for examples sake. I want to test the effect of incubation period ...
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3k views

Randomized Complete Block Design: what if the block random factor is significant?

I'm conducting a two-way analysis of variance. I have one fixed treatment factor and one random block factor and I have $n=1$ for any combination. The thing is that the random block factor is ...
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1answer
193 views

Experimental design vs factorial design

During my study about experimental design, I detect from some examples that factorial design is a sub-step in an experimental design. However till now the idea seems not fully clear for me. What is ...
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254 views

adonis in vegan: limiting permutations when design isn't fully blocked

I have read over the help files and examples online on using adonis with blocked designs but haven't really found a solution to my particular case. I'm fairly new to permutation-based methods so ...
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Question regarding a factorial design and the main effect of one of its factor

Suppose we consider the following $2^4$ factorial design with factors A, B, C and D in the usual order. $Block1 - (0,0,0,0),(0,1,0,1),(1,0,1,0),(1,1,1,1),(1,1,0,1),(0,0,1,0).$ $Block2 - (0,0,1,1),(...