Tagged Questions

1
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0answers
23 views

When to average samples?

My question is when to average samples or when it is allowed to apply a mixed effects model. I have the following constellation: there is a cell-line experiment conducted in a 96-wellplate, meaning ...
2
votes
1answer
68 views

What does R mean by “unbalanced design”?

I think this means an unequal sample in different conditions. But it seems to mean something else. . . I have a data set like below ...
1
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0answers
61 views

Expected value of sums of squares of a blocking factor in a split plot design

How can we show that in a split plot design, the expected value of the sum-of-squares of the blocking factor has expected value equal to $k\sigma^2_{\text{block}} + \sigma^2_{\text{error}}$? I tried ...
1
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0answers
31 views

Help in validating my experiment design

I've devised an experiment plan for an experiment in the domain of cognitive science, but I'm not 100% sure, if my idea about statistical analysis is correct. I'm performing this experiment for my ...
0
votes
1answer
215 views

Determining if a set of experimental results is statistically significantly different from zero?

We have a dataset resulting from an experiment with a genotype A and a genotype B, which underwent either treatment X or no treatment Y, for four total sample groups. Each sample group had only three ...
1
vote
1answer
117 views

Combining between and within-subjects designs?

I have a two by two design. Ideally I would run the whole thing within-subjects (all participants get all conditions) but the procedure is too long. I could run one factor between-subjects (each ...
2
votes
2answers
165 views

Partial, adjusted or Type-III SS of factorial experiment in R

The partial SS for two factor (N and P factors) factorial experiment with interaction can be calculated as: \begin{eqnarray*} \textrm{SS}\left(N_{i}|\mu,P_{j},\left(NP\right)_{ij}\right) & = ...
4
votes
1answer
81 views

What kind of experiment might Hiawatha have designed?

I am trying to understand the poem Hiawatha Designs an Experiment because it looks like the kind of in-joke that it would be nice to get, as a statistician. Here is what I would like to know: ...
3
votes
2answers
223 views

How to deal with repeated measurements in the same condition of a factorial experiment?

I am in Psychology and trying to explore the utility of mixed modeling for analyzing my repeated-measures data in a factorial experiment. The primary reason for using mixed models is that I would like ...
2
votes
1answer
98 views

Should I use ANOVA to analyse this experiment?

We performed an experiment on bacterial growth whereby optical density was recorded for three flasks of E. coli bacteria every 30 minutes for 4 hours. 2 flasks upon the 2 hour mark were inoculated ...
1
vote
0answers
112 views

Survival analysis w/ repeated observations of experimental and control units within periods of differing size & trends over the periods

I have an experiment called Fear Conditioning Acquisition Protocol. We expose mice to subsequent white sounds followed by short electric shocks through the floor. Our aim is to let them learn to ...
1
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0answers
256 views

Cross validation using experimental design methods?

I have a question about using experimental design methods for cross validation in a non-conventional approach. I will use an illustration to explain the question. Imagine you have 100 time series ...
3
votes
0answers
126 views

How to test for differences in binary score data?

I have data from a human subject study that was setup as a 3x2 (system by task type) experiment, with 24 participants. Each participant completed 6 tasks in all, one using each of the 3 systems, and 2 ...
1
vote
2answers
104 views

How should I analyze this design with no replication?

I have data from an experiment where I measured the $CO_2$ from: 4 different dissolved organic carbon (DOC) solutions each at 4 different concentrations each in light and in dark. Each ...
3
votes
0answers
290 views

How to choose between nested or split-plot analysis of variance?

I am having serious problems understanding the type of design I have, I would appreciate any help you can give me to understand it: I have 324 data points, and four factors: ...
3
votes
2answers
314 views

How to correct for inter-experimental variation in cell culture research?

I am testing cell cultures. I grow cells in a "control media" for 2 weeks. During these 2 weeks, the cells produce an antibody, and at the end of the 2 weeks, I measure the levels of the antibody. ...
2
votes
0answers
305 views

2x2x2 plus control group: nested ANOVA?

I recently ran an experiment assessing the impact of three system factors (factor A; factor B; factor C) on user attitudes (4-item scale). Each system factor had two levels (high vs. low). As a ...
1
vote
0answers
131 views

Advice on formula for factorial, blocked (possibly) repeated measures anova in R

Pardon my ignorance, but I really need some help figuring out how to analyze a dataset. Basically the experiment is replicated among 8 blocks, with two treatments (...
2
votes
2answers
173 views

Normalization in pairwise hypothesis testing

I'm reviewing a conference paper (not a stats conference). The authors have done some funny things with their methodology. The experiment setup has 4 treatments, each applied to the same 30 subjects. ...
3
votes
1answer
162 views

Moving from RCB to CR design, how much bias is introduced?

We designed a RCB experiment and assigned the factor levels to the experimental units randomly inside each block. Let's pretend we changed our mind and we would like to go for a Completely Randomized ...
2
votes
0answers
131 views

Initial conditions of experimental units in Completely Randomized Design

Since I had no answer to the second part of this question I would like to ask it again providing some more infos I gathered in the meantime. Context We are designing a complete randomized trial in a ...
1
vote
1answer
108 views

Balance between randomization, interspersion and even initial conditions of experimental units

We are setting up a manipulative experiment in forest where we will test the effect of management on a number of health indicators. We have 1 factor, 3 levels, 3 plots each replicated 3 times; ...
3
votes
1answer
3k views

What is the difference between 2x2 factorial design experiment and a 2-way ANOVA?

What is/are the difference(s) between 2x2 factorial design and 2-way ANOVA? Do they have the same assumptions?
2
votes
0answers
79 views

Analysis of multimodal metric response variables linked to a categorical variable

my level of stats is kind of restricted to some undergraduate courses. Anyhow I received some data from a planned experiment. Basically it is about to test the shear strength (interval scale) for ...
1
vote
0answers
114 views

How to deal with this design?

I have an experiment with 3 biological factors (dev, dev_stage; reg, brain_region; gen, ...
2
votes
1answer
692 views

What an experimental design is this?

I collect blood from one human (donor), separate leukocytes and put $2\times10^6$ of them per each well of five: well 1: $2\times10^6$ Lk (leukocytes) well 2: $2\times10^6$ Lk well 3: ...
5
votes
6answers
14k views

What is the meaning of an F value less than 1 in one-way ANOVA?

What does it mean if the F value in one-way ANOVA is less than 1? Remember the F-ratio is $$\frac{\sigma^2+\frac{r\times\sum_{i=1}^t \tau_i^2}{t-1}}{\sigma^2}$$
2
votes
1answer
225 views

Individuals standard deviations and/or standard errors for groups after implementing ANOVA?

I've seen couple of articles reporting individuals standard deviations and/or standard errors for groups even after implementing ANOVA. My understanding is that groups SE's should be based on ...
2
votes
1answer
277 views

What is the proper ratio of mean squares for a two-level nested ANOVA?

I would like to analyse the following type of experiment using a two-level fully nested ANOVA. We have mice of two genotypes (Group factor) and for each of the genotypes we take a certain number of ...
4
votes
1answer
184 views

How can I treat blocks in a split plot design?

In a field experiment involving crops, what is the difference in considering block as random or otherwise as fixed factor? As far as I understood, random means that conclusion can be extended to other ...
6
votes
2answers
2k views

ANOVA on binomial data

I am analyzing an experimental data set. The data consists of a paired vector of treatment type and a binomial outcome: ...
1
vote
1answer
695 views

Unbalanced repeated measure design for the given data?

I have 3 factors factor1 (treatment) with 2 levels (control, stress) factor2 (Variates) with 12 Levels (Var1, Var2,....Var12) factor3 (Time) with 12 levels (Week1, Week2,..., Week12) The treatment ...