ANOVA stands for ANalysis Of VAriance, a statistical model and set of procedures for comparing the means of groups of related data. Generally the independent variables in an ANOVA analysis are categorical, not continuous.
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Dummy variables in multiple regression, why use an intercept?
When performing a multiple regression with dummy variables, is it really necessary to include an intercept term in the design matrix?
By dummy variables, I mean indicator variables; a one in the ...
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39 views
Is my random variable affecting my response?
I performed an experiment on coral colonies (10 colonies, randomly chosen in repeated measurements); manipulating aragonite/carbon chemistry and temperature (fixed effect) to analyse effects on the ...
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30 views
“effects not estimable” error in R aov
I have data on the effect of treatment on leg shaking. I reused several individuals so I want to know
Is there a significant effect of treatment on shaking
Do the reused individuals present some ...
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1answer
17 views
Insignificant block effect in two-way block design
I used a two-way ANOVA to analyze data collected in a randomized complete block design:
Y~Treatment+Block, where blocks represented spatial units
Whereas Treatment had a significant effect on Y, ...
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1answer
34 views
In a mixed two-way ANOVA, why does a Groups x Intervals interaction decompose under SSwithin and not SSbetween?
Say I've got three treatment groups, and I measure them at three time points. Since the interaction in question involves both the groups (which occur between subjects) and the time points (which occur ...
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20 views
Repeated measures ANOVA in R for non-orthogonal design
I have data from a two-factor within-subjects experiment design where the conditions are not orthogonal. Factor one (Location) has three levels; factor two (Stimulus) has three levels, one of which is ...
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32 views
Experimental design for complex temporal pair interaction data
Context: I am faced with what I believe is a non-trivial modelling problem that I have been assigned as part of my post-doc. My expertise is in the area of graph / network theory so I have found ...
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0answers
12 views
Are the sequential sum of squares appropriate when treatments must be applied in sequence?
I'm working with some modeled future stream flow data that was created in two steps. First, future precipitation predictions (at certain points in a watershed) were created by running historical ...
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1answer
28 views
Difference between disease conditions by non parametric Anova
I've the following simplified data as shown.
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1answer
60 views
R: Greenhouse-Geisser in Anova from car package
i have a question concerning the output from {car} Anova. I want to run a simple 2x2 repeated measures ANOVA using the multivariate approach. I can run the (modified) example from the Anova {car} help ...
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1answer
35 views
Simple Mixed Model with 1 Fixed and 1 Random Effect
I have various datasets I need to analyse regarding soil properties, all in the same fashion, with one fixed effect (which is a position along a transect, indicating different land uses). Now my main ...
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2answers
339 views
How are regression, the t-test, and the ANOVA all versions of the general linear model?
How are they all versions of the same basic statistical method?
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3answers
48 views
When do Post-hoc tests require an adjustment for multiple comparisons
What happens to the Type 1 error rate, the Type 2 error rate, and Power if you do
not adjust for multiple comparisons when you should? What happens to these as a result
of using something like ...
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1answer
63 views
Two-way ANOVA, what to do next?
I used a 3x2 between-subject ANOVA to examine the effect of colour (three levels: colourless, light red, and dark red) and odour (odourless or not) on perceived sweetness. The results indicated ...
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1answer
60 views
ANOVA with 4 factors, 1 covariate & 500 subjects
I'm using SPSS and this drop-down menu: Analyze -> General Linear Model -> Univariate.
...
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1answer
51 views
What does it mean to have negative values for both lower and upper bounds on a 95% Confidence Interval on ANOVA?
My data shows 95% CI = [-1.07, -0.40], what does the negative sign indicate and how do I interpret the data? as I think it is significant for not capturing the value of 0.
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1answer
43 views
ANOVA result indicated that there were sig. differences while Tukey post-hoc test revealed that there were no statistically sig. differences [duplicate]
I was conducted one-way ANOVA analysis to examone the level of knowledge shaorng among the employees based on there age differences. One-way ANOVA indicated that there were significant differences in ...
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0answers
46 views
Which ANOVA is most appropriate?
So, I have a question for a proposal and I'm fairly certain I'm getting an incorrect answer from our local "stats guy". For the record, it's archival data so I can't change the items (which aren't ...
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2answers
107 views
Using lmer for repeated-measures linear mixed-effect model
EDIT 2: I originally thought I needed to run a two-factor ANOVA with repeated measures on one factor, but I now think a linear mixed-effect model will work better for my data. I think I nearly know ...
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1answer
22 views
ANOVA determining percentage of variation
The Financial Review wished to estimate the amount of annual government spending using tax revenue and level of nationwide debt. Data from 1958-2008 (inclusive) was used. All variables were measured ...
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2answers
71 views
Help with Anova of categorical and continuous variable in R and SPSS output
I am having some trouble running an Anova on categorical variables in R and matching SPSS output. What I need to do is run an anova on the dataset below (its a made up data set). But, I need to know ...
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0answers
26 views
ANOVA uncertainty
If I have 10 classification accuracies for 3 different parameter, and I perform an ANOVA test which yields F=1.19 and Prob>F 0.3201. The parameter value indicates the number of features. Does that ...
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22 views
ANOVA for comparing methods: how to order the data
I'm going to run a series of tests for comparing different methods and combinations per two of those methods. And I was wondering how I'd best order the output so that I can easily use it in an ANOVA.
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21 views
How I can find the values of $n_i$?
Consider one way ANOVA model
$$E[y_{ij}]=\mu+ \tau_i, \, i=0,1,2,3,4;\,j=1,\dots,n_i$$
It it is known that $n_0+\dots+n_4=18$ and we want to estimate the pairwise differences $\tau_0-\tau_i$ ...
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33 views
GLM with unequal sample size
I am trying to figure out how to run a GLM with a poisson distribution in R. The data has 4 treatments: A(n=16), B(n=17), C(n=16), D(n=20), and 2 time periods. This data is count/area so there are ...
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1answer
34 views
Repeated-measures error in R ezANOVA using more levels than subjects (balanced design)
I'm having a problem running a repeated-measures ANOVA in R using the ezANOVA function.
I have data from 18 subjects - each subject participated in 3 conditions, ...
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41 views
Two-way anova with interaction term: what is the point of a post-hoc test?
I have a statistics interpretation question. I've recently performed a two-way anova to identify an interaction term between my categorical independent variables (genotype + temperature) that ...
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1answer
59 views
Post-hoc for 2x2 mixed design ANOVA using SPSS
I am analysing an experiment run with 20 participants using a 2x2 mixed design ANOVA. The experiment has
one within subjects variable A with two levels (a1, a2)
one between subjects variable B with ...
2
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1answer
63 views
Advice on the statistical analysis of clinical data using summary statistics, t-tests, ANOVA, and linear regression
I need some help with the statistical analysis of a study of a particular surgery to remove a particular cancer. I am using the statistical program R to conduct my analysis. My data are saved in the ...
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1answer
42 views
What factor (trials or blocks) to use in a repeated measures ANOVA
I am conducting a psycholinguistic experiment. Each trial consists of the subject responding to a word by pressing a button.The design of my experiment is as follows:
5 blocks of a 100 trials each ...
2
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1answer
67 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
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22 views
How to Partition An Interaction SS in ANOVA
I'm a new user of R and I'm trying to replicate Table 6.18 on page 262 in Statistical Procedures in Agricultural Research, By K. A. Gomez and A. A. Gomez. New York, Chichester, etc.: Wiley (1984). ...
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1answer
73 views
Can I use t-test for interaction in a two-way factorial ANOVA?
I have a two-way factorial design, with factors treatment (A vs. B) and time (T1 vs. T2). The same subject was measured twice, at T1 and T2, so I have repeated measurements. I am interested to see ...
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1answer
48 views
How can I perform post-hoc tests to the ANOVA performed during K means clustering?
If I have highly dimensional data and perform k means clustering, I can end up with clusters that differ more on some axes than others.
SPSS provides the option to return an ANOVA for each variable, ...
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1answer
39 views
Dealing with outliers when comparing variances with Bartlett's test
I have four different groups (with unequal sample sizes of 100 to 120) and want to test if the variance differs.
For ANOVAs I used the winsorized mean to get a more robust estimate and I am wondering ...
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1answer
32 views
How to prove the number of distinct distributions in a group of distributions?
Let's say we had 5 distributions: A,B,C,D,E.
An ANOVA test would tell us whether or not all of the means are equal, and thus a low p-value would mean at least one of the means is unlikely to be ...
3
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1answer
54 views
Poisson Repeated Measures ANOVA
The following is a general background into my data analysis problem:
I am working with count data that is non-normal.
Data was collected at 2 time periods.
I am interested in comparisons of species ...
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1answer
35 views
Efficient way to run multiple ANOVAs on subsets of data
I have a data set that is repeated-measures ratings of four devices (two two-level variables) for 6 dimensions (ease, confidence, comfort, control, size and fit), with a two-level between-subjects ...
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1answer
30 views
Evaluating features and similarity measures
I am currently developing a classificator, which is supposed to classify into a number of classes. For this purpose I am
designing some features and similarity measures which I might use for a later ...
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1answer
48 views
ANOVA analysis with only mean and standard deviation
This is probably a silly question, but how can I run ANOVA using only the mean, standard deviation, and the sample size?
i.e.
...
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1answer
59 views
2x3 ANOVA interaction no longer significant after including a covariate?
My experiment had a 2x3 design with one covariate. If I analyse the results using an ANOVA, I get a strongly significant interaction between the two main factors (p<.001). If I add the covariate ...
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28 views
What kind of statistical analysis to use for a homework paper? Anova?
I am writing a paper where I have to pretend to have conducted an experiment. Each of the experimental groups and control has different people.
There are 8 experimental groups and 1 control.
1a 1b ...
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25 views
ANOVA with semi non-independent data
Nectar accumulation in plants is induced by Wounding, and also modulated by the amount of Light reaching a plant. We were asking if nectar response to those factors were localized (in the same branch ...
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2answers
110 views
R p-value half to SPSS rANOVA
I have done rANOVA in SPSS and then in R and got two different p-values from the same model. While SPSS gives 0.032, R gives 0.0162, which when rounded is a half. Other data are exactly the same.
1. ...
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26 views
Calculating differences between groups and across time (age)
Let's say I have data of one variable $V$ measured for two groups of individuals ($a$ and $b$) and I want to see whether there is a significant difference between them and over time, i.e. $V_a$ stays ...
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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 ...
2
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1answer
69 views
Why is ANOVA interaction no longer significant after including a covariate?
I have initially run a 2x2x2 Anova and found some significant interaction between the independent variables. I then ran a ANCOVA where I added a covariate. I am confused with how to interpret the ...
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34 views
How to avoid regression to the mean in a simple comparison
This is a pretty simple question but I haven't been able to find a clear answer to it. I have some data from a behavioral experiment taken under two conditions (A and B); within each condition, each ...
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Can we assume that the true variance is equal to observed variance minus 2 multiplied by (cov)2
The variance covariance theorem is somewhat difficult to be understood. Does it really work in the context of standard variales.
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1answer
31 views
Blocked repeated measures ANOVA in R
I am trying to test if richness varies by treatment (Severity) over time (Block) using a repeated measures ANOVA in R. Any suggestions on how to do this correctly? I have tried, but get an error ...
