The design of experiments (DOE) is the study of how to structure an information-gathering exercise where variation is present. In statistics, controlled experiments are usually implied, meaning that study units are randomly assigned to conditions where levels of a variable have been independently ...

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Handling the “positive bias” in percentages of positive variables

Say we run an experiment and notice the following impact on a variable of interest (one row per experimental unit): ...
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24 views

Analysis of reaction times with missing data by trial/item

I have a developmental psychology study with one between factor (age) and two within factors (scale-3 and difficulty-2). I recorded reaction times but have eneded up with a lot of missing data for the ...
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How to estimate the concomitant variation

Is there a formula/sofwate solution to estimate the concomitant variation for a 3 factorial experimental design with one dependant variable?
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9 views

Account for Repetition in Experimental Design when testing variants of an image

In my experiment, an image is presented in five different ways to the test person. The person then has to do some task like "point to the red flower in the image" and I measure the time taken to check ...
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What is cross-lagged panel design?

The slides for my statistics lectures explain various experimental designs such as single-strata, cross-sectional and longitudinal. Unfortunately, the diagram for Cross-lagged Panel Design is very ...
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Same mean, different variance - test?

I have conducted an experiment where I am interested in how well different models for directional hearing works. For each model a sound is presented to a test subject, and the test subject expresses ...
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2X2 ANOVA: low power, statistical significance for only 1 IV, medium-low effect size

BACKGROUND: I run a 2X2 Between-Subjects ANOVA. I obtained: a low power (< 0.30) for both Independent Variables a not statistically significant result for one of the Independent Variables. ...
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12 views

Mean sum of squares and products according to source of variation in ANCOVA from R

How to get the mean sum of products using R to populate an ANCOVA table as given in the following link? Analysis of Covariance Table for RBD Ryy, Tyy and Eyy can be obtained as follows using ...
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15 views

Analysis of measures of difference

Let's say I want to measure the width of a road using a measuring tape. I've drawn a crap diagram here: Rather than measure the distance directly, I decide to be obtuse and measure the distances ...
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Applicability of survival analysis (using Cox proportional hazards) to question of interest

I have started down the path of using cox PH models to try to understand which variables are driving time-to-migration (event) in my study system. My system has two groups (A,B) of animals that ...
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15 views

Multivariate GLM or MANOVA or other alternative for 2x2 repeated measure experiment?

I am trying to get my head around the right choice of experimental design and analysis for a collaborative software I have created and would like to evaluate. The software allows groups to conduct a ...
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25 views

Interference in experiment with block design

I'm designing an ecological experiment to test how 2 treatments (one manipulated, and one non-manipulated control) effect fish density at at their respective locations. The experiment will be done in ...
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Two nested random factors, planing an experiment

I'm planning an experiment (described below), and I want to be sure that the experimental design is correct, and I'll have no trouble later on when analyzing the data. I want to know if the ...
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How to design experiment with 1 IV (2 levels) and 2 DV's

My groups are control and alcoholics. I want to measure them based on an experiment that has 2 conditions: go (press button after x when you see o followed by x) and no go(when o appears but any ...
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103 views

outlier detection: area under precision recall curve

I would like to compare outlier detection algorithms. I am not sure if area under roc or under precision recall curve is the measure to use. A quick test in matlab gives me strange results. I try to ...
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11 views

Convenient plot size detectable difference vs Least Signifcant Difference

I am curious how Hatheway's (1961) Convienient plot size calculation, once rearranged to solve for the detectable difference, relates to a standard LSD calculation: $$ d^2 = \frac{(t_1 + t_2)^2 \times ...
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Estimate causal effect with lots of missing values

This is a generic question. Suppose you run an experiment with units randomized between a treatment and a control group. Imagine the response rate is very low in each group, say, below 10% and with a ...
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19 views

Repeated measures anova in R

I have a dataset containing percentage scores for 15 participants. There are two observations for every participant, one with an intervention and one with a placebo in a double-blind design. Each ...
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30 views

How to deal with statistically insignificant factors?

I used $2^4$ factorial design to screen significance of the factors $A$, $B$, $C$ and $D$. It turned out that $A$ and $B$ were significant, whereas $C$ and $D$ were not. Since there is no need to ...
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7 views

Expanding an experimental design

I have completed test work following a randomised response surface (multi-factor) experimental design (Central Composite Full) but have found that my levels for two of the factors are not broad enough....
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How to measure extraneous and confounding variables?

The test-re/post/test methodology entails establishing a baseline, introducing a condition and measuring the effect size. The condition is known. But whether or not it yielded some changes, is what ...
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Designing paired samples of Group A vs. Group B+C

I have decided to use a strict bioinformatics algorithms that under its way calculate fishers exact test. My samples are to parentals A1 and A2. These were treated and subgrouped into 14 clones. Two ...
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17 views

What family of GLM when response is Bray-Curtis dissimilarity? Should I use “adonis” instead?

I have some questions about testing for effects of different experimental levels on community similarity. I'll explain my planned experimental design before I ask the questions: I have two methods ...
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General strategy of confounding design

Example: Suggest a confouding scheme for a $2^8$ experiment in 16 blocks of 16, assuming that all 2-factor and 3-factor interactions are to be estimated. Please find the confounding design. Question: ...
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Completly Randomized Trials versus Incomplete Cubic Lattice

I have a 2x2x2x2 design, which I wish to balance. Previously, the binary factors appeared throughout the experiment with a 50% probability, which each have to result in a uniform distribution. I am ...
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sample size for multi-arm randomised control trial measured over time

I would really appreciate any advice on calculating a sample size: This study involves looking at a specific disease, then performing a randomised control trial in two different geographical areas ...
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What is the relationship between LATE and TOT?

My understanding of LATE was that it was the effect of a treatment on individuals who were induced to be treated by the experiment. That is, the effect on compliers. My understanding of Treatment-on-...
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How to aggregate many simulation runs for curve-fitting?

I have results from about 200 runs of a simulation model. The results contain a stochastic response variable which I want to approximate with a curve-fitting approach. So far, I have opted for ...
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What type of statistical models would be useful for evaluating an athlete's performance?

Suppose a performance athlete wants to use statistics to design an optimal exercise regimen. The goal of the statistical model should be to essentially maximize the performance of the athlete by ...
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Power analysis for two-sided non-compliance

Using Chamber of Commerce data for a small town, a local non-profit wants to evaluate the effectiveness of direct mail vs. email for getting business owners to contact the non-profit. We aren't ...
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1answer
34 views

Does descriptive research have dependent varibles?

I am doing a research proposal for a descriptive study to identify the health beliefs and perceptions among women to mammography breast cancer screening. I am using a Likert scale that is divided into ...
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32 views

Why does R power.prop.test & R prop.test show inconsistent results?

I am a bit confused by the differences I am seeing between R's power.prop.test & prop.test functions. To estimate the sample size needed for an A/B test I am conducting I am using the following ...
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21 views

How do I test the parametric assumptions of a split-plot ANOVA?

I have an RCBD split-plot experimental design for testing the effects of drought, tillage, and nutrients on plant biomass: Block = random factor (2 blocks of 10 plots each, total 20 plots) Drought = ...
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Do I still need ergodicity if I have multiple/infinite time series of the same data generating process?

The main reason we need ergodicity (and therefore stationarity) is, as Shalizi puts it: The ergodic theorem is important, because it tells us that a single long time series becomes ...
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Nested mixed experimental design with crossed factors for laboratory validation procedure: how to model it?

I have been asked to analyze the following laboratory experiment: 14 donors’ red blood cell samples are typed for rare antigen-asset recognition by an automated procedure (machine), which returns a ...
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the Randomised Complete Block Design

I got the following output using the Randomised Complete Block Design: ...
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One-way Fixed model

Duppose we have 12 treatments, and to start the experiment we choose these treatments, randomly. However, after selecting one treatment, all the samples are gathered and we shift to the next treatment ...
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47 views

What is my study design

I have two sample groups and I will not be manipulating the participants in any way so this is not an experimental design. However I wish to compare the results of the two samples (between subject ...
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1answer
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What is the proper way to increase power when randomizing at the village level?

Let's say that we have a hypothetical RCT with the following information: --We are interested in seeing whether a particular belief held among some individuals in a developing country can be ...
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Pros and cons of various designs

Help me with this question. I'm clueless. CROSSOVER DESIGN PROS- Gain in precision- compare approaches within students, so variation between students is eliminated. CONS- Susceptible to carry-over ...
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How to correctly analyzed a mixed within-subjects/between-subjects design?

I recently ran a perceptual study in which I aimed to measure how emotion recognition accuracy from whole-body motions changed when two type of body representations were used. Five actors Ai with i=1,....
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Confounding variable that is the focus of experiment

The wiki defines confounding variable as an extraneous variable in a statistical model that correlates (directly or inversely) with both the dependent variable and the independent variable I'...
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1answer
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Ranking Data Comparison

I'm currently analyzing my experimental data and I have a question about comparing two variables. In the experiment I have a question which asks respondents to rank a set of pictures based on their ...
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42 views

When is there a point for using regression with controls to analyze experimental data?

Many randomized controlled trials in economics (and probably other sciences as well?) use regressions to analyze data obtained from experiments. In the simplest setup with binary treatment, assuming a ...
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1answer
19 views

Why use Coded Variables in Experimental Design?

Full-disclosure, I'm not sure if this ENTIRELY on-topic. Often times, most texts will suggest that we code our variables. i.e. If we move from 345 to 350 to 355, we code our variables as -1, 0, and 1....
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20 views

regarding generating synthetic data simulating the real data

We are trying to develop some predictive models. The current scenario is that we have to rely on synthetic data at first since the real data set will not be available quite soon. It is understandable ...
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33 views

Questions about mixed model design with repeated measures/nesting/incomplete design

I have data from a incomplete factorial experiment with repeated measures and potential nesting and am trying to figure out 1) the right way to design the mixed model to analyze the data, and 2) how ...
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10 views

Which analysis do I use for this experimental design?

Seeking feedback from those with a better quantitative mind than my own! Currently preparing my doctoral research proposal. I want to determine the impact that various levels of technology (...
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19 views

Regression Discontinuity Design Using Time of the Policy Change as the Assignment Variable

I am trying to study the impact of a policy change on user behaviour. In my context, a new policy is implemented on a specific week. Hence, everyone is exposed to the new policy at the same time. I ...
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1answer
40 views

Experimental Design with Factorial Block Structure

I'm designing a language-learning study with maybe 30 participants. My collaborators want each person to experience both of the methods we're using, so we are planning a crossover design. In addition ...