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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Two-way ANOVA doesn't detect differences between conditions in a specific group?

OK, so let's say we have independent variables Condition (A or B) and Race (1 or 2 or 3). Then say we have a dependent variable X. We can run a two-way ANOVA to find out if there's an effect due to ...
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28 views

Why do we ignore the main effects when the interactions are not significant in a three-way ANOVA?

I'm following an SPSS guide online, and the procedure is to first test for a three-way interaction. In my case there was no sig. three-way interaction. Then the procedure asks me to consider two-way ...
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2answers
112 views

Adjustable sample size in clinical trial

Most clinical trials I see have a fixed sample size. In some cases they have prior data that allows estimating the effect size and the variance or distribution of values, and calculate the sample ...
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57 views

How to analyze data once broken down into gender, race, etc

I have two conditions, Treatment A, and Treatment B. Participants are randomly assigned to a treatment at the outset. Then I run unpaired t-tests on the data to find any differences. BUT I am also ...
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49 views

1 and 2 sample t-tests for plants and soils question!

I have a good friend who has an experiment where he grows different kind of plants on various soils and measures the protein content and weight each week for 5 weeks. His goal is to determine which ...
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31 views

Post-hoc multi-level design analysis

I am developing a model to predict a dichotomous satisfaction measure on festival event participants. Events can last 1 to n days; and participants are grouped in parties of 1 to k party members who ...
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0answers
23 views

Why am I finding greater power with a coarser level of randomization?

I am working on a Monte Carlo power analysis for an experiment about the hiring of teachers in schools. We can randomize the treatment at the school level or at the applicant-school level. I was ...
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1answer
29 views

Why does randomising the order of measurements remove time as a confounding variable?

Say we're interested in the difference in x between Group1 and Group2. We might measure 50 samples from Group1 then 50 samples from Group2. If the accuracy or precision of our measurements change over ...
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6 views

Searching for a term for systematic, universal non-reporting in survey data

I am searching for a technical term to describe a situation I have run into my survey research and analyzing survey datasets. In experimental survey research, systematic under-reporting and ...
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28 views

Choosing the correct experimental design

So lets just say I conducted a chi-squared contingency analysis test (I did btw) on 40 separate fish. Each individual fish only went through one treatment trial, where they were subjected to ...
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14 views

Paired studies: possible drawbacks

I have a question regarding paired studies. We are doing a medical study, we have a whole lot of data on a few hundred people and our aim is to study if a different level in one substance is linked to ...
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0answers
15 views

BIBD or IBD or PBIBD

I use block design for discrete choice experiment. While Balanced incomplete block design(BIBD) is considered as gold standard for blocking in choice experiments. However this is not always possible ...
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21 views

Do two-way ANOVA data need to be strictly balanced?

I conducted an experiment of 2x2 between-subjects design. So there is four conditions with the two factors. However, after deleting the data that failed to pass manipulation check, the four conditions ...
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11 views

Ask about measure pretest posttest in different groups

My team members are going to have a blood donation campaign and we would like to see whether the campaign has significant social impact. A group of people will be randomly asked to answer a ...
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16 views

Help with repeated measures analysis in a complex design

I'm looking at a study measuring blood flow in the brain, there are 8 subjects in this study, with 18 measurements each. The measurements are done 6 at a time in three different time points ...
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50 views

Combinatorial Block Designs in Statistics

I am interested in description and references for how combinatorial designs (such as BIBD, Steiner triple systems etc.) are used in statistics (especially in designs of experiments and hypothesis ...
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1answer
14 views

ANOVA table for 4-factor split-plot

Hopefully I can explain this clearly. Reference diagram below if needed. I'm planning a large field experiment that I think will have to be a split plot design. There are six sites (outlined in ...
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15 views

How to Analyze Categorical Data in a Repeated Measures Design?

First post. I've read through similar posts and no one's quite answered it already, so I thought I'd throw my hat in the ring. Here goes: I have a repeated-measures design planned proposes to ask a ...
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4answers
223 views

When does correlation matter when there is no theoretical relationship?

Summary: Correlations does not imply causation has became mainstream. I am interested in understanding what is required for the implication to actually take place. Detailed question: When I have a ...
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11 views

Quasi-experiment with naturally assembled collectives (classrooms): Propensity score matching or not?

I am planning on running a quasi-experiment (pre-test post-test non-equivalent groups design) that involves two treatment groups that are subjected to different treatments (X+ & X-) and one ...
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14 views

Why does a blocking design require balancing across blocking levels

Why does a blocking design require balancing across blocking levels, say the following design is valid: ...
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0answers
11 views

Experimental Design Optimal allocation to treatment

I have trying to design an pre-post study on the effectiveness of a particular media platform in inducing behavior change. The 700 households are distributed in 6 geographical clusters. They have ...
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1answer
20 views

Experimental Design: Matching Control and Experimental Groups

I am running a health intervention among children. There are 6 clusters of neighborhoods that are included in our study,each with 48 households. The households are being measured on 7 key variables. 4 ...
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1answer
42 views

Dichotomizing continuous variables for an EXPERIMENT not a survey

I've aware of the many issues/pitfalls with splitting continuous variables in survey research. Nothing I have read addresses whether doing so to create groups which will then be assigned to tx ...
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30 views

Repeated measures ANOVA of an experiment

Here's something that has bugged me a little bit and is quite fundamental to running statistics in experimental settings. Say I run a psychological experiment with 1 categorical IV (load: 4 levels) ...
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0answers
22 views

PCA to look at relationships between pretest - posttest changes?

I ran a pretest posttest experiment with two groups. I am interested in looking at how the changes in the measured variables (for example: levels of depression, levels of empathy, levels of anxiety) ...
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1answer
40 views

Regression discontinuity design with multiple cutoffs

When we have an RD with multiple cutoffs, and we pool all observations and estimate the treatment effect across cutoffs, what does the pooled estimate identify? I have found one paper using a RDD ...
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2answers
45 views

Can we use weights in lme as a covariable?

This question might be a duplicate, but a colleague and I have trouble understanding previous answers about the use of weights in lme. So in simple terms: We have an experimental design with 2 ...
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Terminology for comparing anwers to a set of reference questions

I´m conducting a questionnaire in order to examine the behavior of drivers of electric vehicles when providing information, such as parking time, to a charging station. For several reasons it is ...
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2answers
52 views

Using Kruskal Wallis vs One Way Anova with small sample size

I have an experiment with one factor and five levels. The response is proportion of conversion (ex: 1/11, 1/8...). Doing a power analysis: ...
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13 views

Pairwise Learning to Rank - detecting detrimental changes

The idea behind Pairwise Learning to Rank is that if you have a set of search results then a clicked on result can be used as training example to indicate that it should rank more highly that the ...
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0answers
20 views

Threshold for true experimental status?

This has been bugging me for a while now. I've read numerous sources but I can't really find a definitive answer. Most textbooks deal with generic designs but don't really address designs that ...
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29 views

User Study Setup: Correct selection of tasks

I'm struggling with the problem to design a formally correct user study. I have the following circumstances: I want users to assess the (subjective) usefulness of a -so called- trail result. That ...
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11 views

Finding redundant parts of a data set for training a nonlinear model

I like to train a nonlinear model based on a data set $D_1$,..$D_n$, where $D_i$ is collected by doing experiments $E_i$. It is possible that $D_i$ is redundant given $D_j$ and $D_k$. Since doing an ...
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0answers
73 views

Regression on unbalanced two-way with interaction

I am developing my own algorithm to calculate it for me. I am interested in type III SS and using the overparametrized design matrix to estimate my parameters vector and then proceed to the cubic ...
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23 views

Have I interpreted the effect of a confounding variable correctly?

I'm interested in whether feeding rate differ between two species of birds, Species A and Species B. However, tide also affects their feeding rate, and so tide is a confounding variable. In the plot ...
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12 views

Predicting individual treatment effects as the difference between predicted outcomes with and without treatment

To provide some context, I am trying to (a) identify the best ad to increase support for a particular issue among a large group of people, and (b) identify the people most likely to respond positively ...
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21 views

Assign the tree species most representitive of a specific size class

I am replicating another study in which trees were assigned to a class based on diameter. The most representative species of each class was identified for each plot sampled. The classes are sapling ...
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0answers
14 views

How to make Fractional Factorial designs with constraints?

I want to make a Fractional factorial plan of $2^{100}$ with the following additionnal constraint : $\sum_1^{500} I_{x_i=1} =5$ and $\sum_1^{500} I_{x_i=-1} =95$ ; where $x_i i=1,...,500$ are my two ...
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0answers
41 views

Are Latin hypercube samples uncorrelated

I understand the basics to Latin hypercube sampling, such as implemented by the algorithm LHSA mentioned in the book Design and Modeling for Computer Experiments. But I'd like to make sure: 1, n ...
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0answers
14 views

Need help setting up a model and running a test for significance

new poster here. I've taken very basic stats classes so I would like some help setting up a model testing the significance of an Act that was passed by the US gov't recently utilizing real data. ...
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26 views

How should you perform a manipulation check for multiple items that should belong to one of two groups?

Suppose I have 8 creatures that participants rate on my YuckFactor scale. I chose 4 cute animals to be part of a LowYuck group and 4 ugly bugs to be part of the HighYuck group. How can I test that ...
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44 views

Required sample size with unequal variances

I have a setup with equal sample sizes ($N_1=N_2$) from two groups (sample means $\mu_1$, $\mu_2$), but different variances $\sigma_1^2$, $\sigma_2^2$ in both groups. If the variances were equal, ...
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1answer
28 views

Residual vs fits for 2-level factorial design

So I'm analysing a 2-level factorial design, and get the residual vs fits plot below. I don't understand why it's symmetrical around 0. In any form of linear regression I've learned that the plot in ...
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1answer
26 views

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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17 views

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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19 views

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 ...
2
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1answer
27 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 ...
3
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1answer
48 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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45 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 ...