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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How can I determine statistical significance in an A/B test in which the KPI is dependent upon two variables - one bernouli and one continuous?

In my work in online marketing, we frequently run A/B or multivariate web page tests. The Key Performance Indicator for these tests is overall Revenue. The treatment that nets the most revenue, either ...
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15 views

Tukey's HSD after a randomized block design in R

I want to run a Tukey's HSD on my data after performing a three factor anova with block as a fourth random factor. The anova works fine in R, using the following code, ...
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13 views

Multiple Comparisons after an ANOVA

I want to perform a Tukey's HSD after performing a three way anova with blocks as a fourth random factor. I am able to perform the anova using aov(dv~f1*f2*f3+Error(block/(f1*f2*f3)), data=*.txt). ...
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Guide / tutorial for design & analysis of experiments in retail settings

I want to develop my skill set in the design and analysis of experiments in retail, where we conduct experiments (introduction of new package, new product, discount, etc.) in test stores while ...
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10 views

sequential testing and hierarchical tesing

With respect to the hypothesis testing, I once heard sth such as sequential testing, hierarchical testing, and multi-level testing. But I could not find a good reference discussing these topics. Any ...
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22 views

Response surface of a particular discontinuous function

I have a function IR that depends on several (maybe 100) input random variables. I know ...
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1answer
37 views

Designing an experiment where participants see all levels of one factor, but not of the other

Let's say I have an experiment with two factors A and B, each with a number of different levels. I want participants to see all levels of factor A exactly $n$ times, never see a level of B twice ...
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10 views

Homogeneity of Variance, 2 Way Completely Crossed Design

I am looking for some advice as to how I might handle having an unfavorable Levene's test outcome, that is to say a highly significant value. DOE Various containers with water were microwaved for ...
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1answer
75 views

Constructing one-ninth fraction of the $3^{5}$ design

I want to construct a $3^{5-2}$ design with $I=ABC$ and $I=CDE$ as generators. The complete defining relation for this design is: $I=ABC=CDE=ABC^{2}DE=ABD^{2}E^{2}$. This is a resolution III design ...
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9 views

Effects of reducing number of central points in central composite design?

The central composite design method involves evaluating the experiment at the central point several times (typically 4 times). If this method was used for a deterministic computational experiment, ...
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1answer
62 views

How to compare pre- and post-tests when subject identifier is missing?

My colleague and I are professors and we conducted an experiment in which we would please like some advice on deciding which tests to use in SPSS. He taught 4 classes of students on 2 different ...
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24 views

Checking if improvement is significant. Test design

I have designed two simple tests to check my algorithm. For a set of 40 pictures, 20 people will judge if: Test 1: Object A or B is seen in the picture (i know the correct answer) Test 2: Object A, B ...
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21 views

How to calculate main effects of factors in R with DOE.base and/or FrF2 packages? [migrated]

New to DoE. For the following $2^3$ factorial design coded with DoE.base package in R: ...
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11 views

How to analyze data from two-tiered experiment

I have an experiment where each subject undergoes M sessions of treatment drug & control drug. I have N subjects. How do I 'match/pair' my data together? In particular, lets say that d(n,m) is ...
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16 views

Suggestions for tools or strategies to visually compare results

This is not exactly a technical question related to any method, but this seemed like the best forum to ask this. The question I am asking is more along the lines of experimental data management. I ...
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3answers
102 views

A one-way between subjects ANOVA

I have 3 visualization techniques (e.g., PC, NL and Map). I wanted to evaluate user performance (Time and Accuracy) for these three visualizations methods. I have 9 tasks for participants to perform. ...
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19 views

Estimating the probability of causation based on finding a correlation, including experimental details

Say there is a hypothesis that A causes B (A -> B), and some likelihood that the hypothesis is correct (AB1%). Now, an experiment is run that claims to find a correlation between A and B. What I ...
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3answers
879 views

Why does the standard deviation not decrease when I do more measurements? [duplicate]

I made 100 measurements of a certain quantity, calculated mean and standard deviation (with MySQL), and got mean=0.58, SD=0.34. The std seemed too high relative to the mean, so I made 1000 ...
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16 views

Selecting genes more affected in treatment A than treatment B

We are trying to test the hypothesis that a mild mutation of a gene has few effects on the expression of the transcriptome than complete deletion. Further we wish to test the hypothesis that the genes ...
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21 views

design and analysis of experiments

Kindly recommend some teaching material for "design and analysis of experiments" for the students of biostatistics and epidemiolody. Pls note that the students have only little knowledge on ...
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23 views

Analyzing 3D data: What can be done?

I am new to this kind of analysis, and I want to know what values I can look at in 3D data. The data itself is a 3D volume $(x,y,z)$ with a floating point value in every coordinate. It is a ...
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1answer
37 views

Epidemiology cohort studies question

If we are conducting a cohort study of factors associated with recurrent myocardial infarctions (MI) following the first one, should our study population at baseline include subjects who had ...
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15 views

Calculating variation of one variable within one experiment

I am conducting a preliminary study, where people assess (7-point likert scala) different pictures. Besides asking for my 2 Independent variables (which are the manipulations for my main study, an ...
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29 views

Deep and sparse vs. Thin and dense data collection for curve fitting?

I'm designing a toy experiment in which I'd like to model the 'attractiveness' of a credit card as a function of the interest rate it comes with: Attractiveness will be reported on a 10 point scale ...
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50 views

Is this Poisson regression specified correctly?

I want to ask some confusing in my mind regarding the data analysis: I have conducting the experimental trial in repeated measure by hours as below: ...
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1answer
35 views

Treating factorial design as complete randomized design

Lets say I have 10 different treatments and these 10 treatments can be considered combinations of 2 factors - as in a factorial design experiment. What do I miss if I treat this data as coming from a ...
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28 views

Regression discontinuity and regression to the mean

Regression discontinuity designs aren't susceptible to regression to the mean. I'm not quite sure why, though. The best I can come up with is that regression to the mean is a phenomenon that occurs ...
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29 views

Experiment Design - Randomized Block or Completely Randomized

We have Five litters of rats, each containing four rats. The five litters were randomly selected from a population of litters. Investigators are interested in comparing the mercury content from fish ...
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1answer
24 views

Selecting gene list for subsequent analysis in problematic microarray experiement

I have an experimental design problem and I'm not sure which would the best way to proceed. We have a micro-array experiment in which we compare gene expression profiles between 2 groups of patients. ...
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50 views

What are the trade-offs between a two-factor unreplicated design and a one-factor design with two replicates?

I am interested in the effect of two different factors, $x_1$ and $x_2$, on a response $y$. However, although I'm interested in both, I'm more interested in the effect of $x_1$ on $y$ than I am in the ...
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24 views

Selecting samples for calibation in regression model

I am developing a multiple regression model. Recently I came across a statement that for the calibration set it's "better" to select samples which are uniformly distributed in a response variable ...
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18 views

Identifying a block design

In designing a email test, I have three binary factors (each have two levels, say low-high). Our customers are divided into 5 non-overlapping groups. Is it best to run a randomized block design, ...
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2answers
164 views

Using control variables in experiments?

Why would one want to control for any number of baseline covariates in a situation where the assignment to treatment group is random? My understanding is that randomly assigning treatment should make ...
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11 views

What is an interpenetration design?

I have come about a quote in Groves & Lyberg (2010, p. 859) saying that "(...) both interpenetration and reinterview designs are required to estimate these terms" (referring to estimation of ...
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80 views

Whether the population exists in an experimental study?

In my oral exam one of my teachers asked whether the population exists in an experimental study. I answered: "Yes. the population exists in an ...
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45 views

Sampling using PCA and maximizing variance

In 6 forests, I've 3 variables that I know the values for all trees: $height$, $diameter$ and $density$. I can only cut some trees to know their $mass$. The question is how to choose the trees to cut? ...
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40 views

Determining if experiment data can be pooled from multiple experiments

We have a dataset with Time and Treatment as independent variables, and growth volume as a dependent variable. The experiment was repeated on three occasions, with multiple time points and multiple ...
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2answers
175 views

The $z$-test vs the $\chi^2$-test for comparing the odds of catching a cold in 2 groups

I just read in a rather well-respected (popular) science magazine (the German PM, 02/2013, p.36) about an interesting experiment (without a source, unfortunately). It caught my attention because ...
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2answers
94 views

Correlation or t-test?

Following experimental design was done and some data as shown in table below was obtained: pretest> intervention1> intervention2> posttest > perception survey Number of students=60 Number of ...
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1answer
203 views

How to design experiments for Market Research (with a twist)?

Consider a kind of auction where you are presented with, say, 1000 prospective clients. Based on information about these prospectives--age, sex, race, income, educational achievement and the like--you ...
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18 views

Outcome variable in experimental design

I have been asked to try to operationalize our research question methodologically in an experimental design but since this is my first experience doing so I feel unsure and am looking for some help. ...
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40 views

Unstandardized effect size for two non-equal size samples for experimental design in R

I am trying to calculate the required (unstandardized) difference in between a test and control group of different sizes. I have historical data with transactions for the test group (n=272, mean ...
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24 views

Is a nested log-binomial GLM appropriate for this?

Dependent variable: Death (0 or 1) Independent variables: Dose (0, 10 or 20), Timing(Early or Late), PreviousDVT(0 or 1) Ignoring the Timing variable for the moment, the model I had originally ...
3
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1answer
137 views

How do you “control” for a factor/variable?

To my understanding, "Control" can have two meanings in statistics. Control group: In an experiment, no treatment is given to the member of the control group. Ex: Placebo vs Drug: You give drugs to ...
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1answer
80 views

How to exclude interaction effect in linear regression modelling?

I am working with biological dataset. I am looking for significantly differentially expressed genes that stand out under effect of 3 different factors (e.x. gut microbiota level has/not, tissue, ...
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10 views

Testing hypothesis for multiple groups in two settings

I am testing six groups on six different websites that fall under two categories (responsive websites and mobile websites). Each group contains 10 participants. One group rate one site in one ...
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107 views

Statistical analysis approach for seed germination and viability study

Background: I am a stakeholder in a research project involving seed germination and viability tests for a number of shrub species. The ultimate goals of this project are to determine best practices ...
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21 views

Diallel Analysis

I apologise for the mix-up. Am trying to do a diallel analysis involving three parents in poultry. I tried using SAS05 program but it didnt work, i guess it was designed for diallel analysis involving ...
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29 views

binarization of variable - experimental threshold choice. Is it good approach?

I have some ratings averages values from 1 to 5(users were rating on 1,2,3,4,5 scale). I would like to split them into two classes: credible, ...
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37 views

Is this a split plot?

I have attempted to view the following experiment as a split plot design: 15 undergraduates serve as subjects for an experiment that compares two hypnosis methods. There are two phases to the ...