Tagged Questions
1
vote
1answer
32 views
NLME regression & curve comparison in R. ANOVA p-value
I obtained data of typical time point in two conditions in this shape:
...
1
vote
1answer
37 views
Degrees of freedom ANOVA table for regression
I've calculated the following ANOVA table for a linear regression in R:
...
0
votes
0answers
12 views
ANOVA as Comparision of Means and Regression [duplicate]
ANOVA, ANalysis Of VAriance, is a method to compare means of several variables. At the same time it falls under G(eneral)LM in a sense that it a method for regression and used for regressing ...
1
vote
2answers
105 views
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 ...
10
votes
3answers
798 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?
1
vote
2answers
90 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 ...
2
votes
1answer
75 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 ...
0
votes
0answers
37 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 ...
0
votes
1answer
99 views
Question about reading an output for using ANOVA to compare two linear models
I tried to compare the following two models using "anova.lm()" in R:
...
6
votes
0answers
148 views
Type III sums of squares
I have a linear regression model with one categorical variable $A$ (male & female) and one continuous variable $B$.
I set up contrasts codes in R with ...
1
vote
1answer
76 views
How to interpret a non significant independent variable?
I conducted a regression analysis using R's lm() function. One of the independent variables shows no significance (p = 0.89), which contradicts the hypothesis that is should have a significantly ...
0
votes
2answers
65 views
0
votes
0answers
86 views
Multicollinearity: is a matrix scatterplot enough to rule it out?
I am analyzing an environmental data set containing one response variable (R) and many explanatory variables.
The explanatory variables are either factors (F1, F2, F3) or continuous variables (V1, ...
2
votes
1answer
203 views
How does anova.lm in R calculates “Sum Sq”?
I'm learning R and trying to understand how lm() handles factor variables & how to make sense of the ANOVA table. I'm fairly new to statistics, so please be ...
0
votes
0answers
50 views
Which models should be compared when using the regression formulation of multi-way ANOVA?
I dithered about whether to post this on Stack Overflow or here, but I think the question is more ideological than practical, so please forgive if there's too much technical detail!
I'm trying to ...
4
votes
2answers
562 views
How would you do Bayesian ANOVA and regression in R?
I have a fairly simple dataset consisting of one independent variable, one dependent variable, and a categorical variable.
I have plenty of experience running frequentist tests like ...
0
votes
0answers
44 views
How do I show the difference between two sample groups who participated in the same research
As part of a college research project I gathered data (convenience sampling) for my project. The goal was to show the difference between two groups who were exposed to the same set of circumstance ...
0
votes
1answer
47 views
Testing Independent variables impact during different decades
I am trying to test the impact that independent variables, Growth, Inflation, and Z (good economy for several quarters), have on the presidential vote received by the incumbent party.
My alternative ...
1
vote
0answers
235 views
Comparing model fits or regression coefficients for nonlinear models fitted to different data sets
I have kinetic data measured under several treatments (one experiment per treatment) which can be fitted by several nonlinear two-parameter models, how can I compare whether there there are ...
2
votes
3answers
111 views
What are the problems with doing regression on sample means instead of ANOVA in a time series setting?
I have data from an annual survey which seeks to assess the needs of consumers on a 1 (least important) to 5 (most important) scale. Thus, I have data that looks like so:
My goal is to assess if ...
0
votes
0answers
128 views
Not sure how to work out SSG and SSE on ANOVA table
I have a table that is:
$$
\begin{matrix} & \mathrm{Tyre\, A} & \mathrm{Tyre\, B} & \mathrm{Tyre\, C} & \mathrm{Total} \\ \mathrm{number\, of\, tyres\, tested} & 25 & 32 & ...
1
vote
1answer
59 views
Regression and multiple comparison methods for data where each available category is ranked
I have collected a data from 200 customers on their brand preference of 5 international fast food chain shops. Each customer was asked to rank all the 5 brands from highest to lowest (5 for the most ...
3
votes
1answer
138 views
Measuring effects of categorical factors on binomial outcome with many groups
I'd like to do some analysis of shooting efficiency in basketball when a team is leading (AHEAD) or trailing (BEHIND) by less than 8 points and whether they are HOME or AWAY. Here are a few examples ...
4
votes
1answer
1k views
Linear regression vs analysis of variance: how to explain the difference?
On the Mathematics site an OP who is just learning statistics gave his description of the difference between linear regression and ANOVA and asked if his interpretation was correct. I responded that ...
2
votes
3answers
420 views
Comparing two groups: one-way ANOVA vs. regression analysis with dummy
I am a bit puzzled with the following issue: the outcome of one-way ANOVA test shows that the mean difference of variable y between two country samples is statistically significant. However, after ...
2
votes
2answers
199 views
PCA with all categorical factors prior a regression with a continuous response
I realize that similar questions have already been asked and answered, but I am in need of a bit more detail and specific advice as I am new to PCA and statistical methods in general. My question is ...
2
votes
1answer
87 views
Quantify influence in ANOVA
I have done the following measurements:
Independent Variables IV1 and IV2 with a ordinal scale
Dependent Variable 'DV' with an ordinal scale
Tested 8 different values for IV1 and 6 different values ...
1
vote
2answers
106 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 ...
2
votes
1answer
910 views
Comparing means between two groups over three time points
I have two groups of ten observations each, where the weight are measured at three different points in time. Let´s say baseline, 2 months and 5 months after baseline.
Now I would like to draw a ...
2
votes
1answer
148 views
What is the meaning of operators in regression or anova formulas in R
I was wondering, what is the meaning of operators in anova or regression formulas in R
For example
"+" aov <- aov(x~time+sample, data=data) -> repeated mesures anova?
"*" aov <- ...
2
votes
2answers
1k views
Why do linear regression and ANOVA give different $p$-value in case of considering interaction between variable?
I was trying to fit one time-series data (without replicates) using regression model.
The data looks like follows:
...
2
votes
1answer
105 views
Proper order of variables in unbalanced ANOVA
If you have unequal sample sizes in cells, then the order in which you enter model terms changes your results for sequential or Type I SS. The first variable to enter the model is allocated its ...
7
votes
4answers
600 views
ANCOVA in R suggests different intercepts, but the 95% CIs overlap… how is this possible?
We have a data set with two covariates and a categorical grouping variable and want to know if there are significant differences between the slope or intercept among the covariates associated with the ...
2
votes
0answers
385 views
Using variations of ANCOVA for non-normal distributions
My first question here, hope to be relevant to the community. Im into CS course and a total rookie on statistics, so let me know if more detail is needed and I will edit the post.
I have a problem ...
1
vote
2answers
136 views
Which statistical method should be used in the study of stability of an enzyme?
I did a study monitoring the stability of an enzyme exposed to different conditions over time. Each day for 30 days, an aliquot was taken from each storage sample and analyzed in duplicate. I wanted ...
1
vote
0answers
415 views
How to choose between ANOVA and regression?
I am doing a thesis project evaluating differences in attitudes towards trans students. The only manipulation was which vignette participants read. My variables are as follows:
DV1: First impressions ...
3
votes
1answer
426 views
Using and interpreting type I SOS in three-way ANOVA
My research question is from education: To test whether groups (university, department, gender) differ based on their scores in a test, and whether there are any interaction effects, I'll do 3-way ...
0
votes
1answer
137 views
Optimal polynomial order in equality-constrained linear regression
In fitting a polynomial $p_N = \sum\limits_i^N a_i x^i$ to my dataset $(x,y)$ using a least squares criteria, I'm interested in determining the optimal polynomial order $N$. The caveat is that, owing ...
1
vote
0answers
120 views
Interaction terms and BUGS
It occurred to me that how one writes an interaction term in BUGS depends on the types of predictors that are "interacting". Suppose data that are long (rather than wide). Then, a model with an ...
7
votes
1answer
132 views
Technical variation versus real signal
I'm testing for difference in a continuous outcome under three different conditions.
Under condition A I take a measurement of the outcome. I do this twice for the same sample. Example values could ...
3
votes
2answers
358 views
Are ecologists the only ones who didn't know that the arcsine is asinine?
Proportion, ratio, and percentage data is very common in ecology (eg, % of flowers pollinated, male:female sex ratio, % mortality in response to a treatment, % of leaf eaten by an herbivore). An ...
8
votes
2answers
2k views
Regression vs. ANOVA discrepancy
I was always under the impression that regression is just a more general form of ANOVA and that the results would be identical. Recently, however, I have run both a regression and an ANOVA on the same ...
1
vote
1answer
387 views
Why don't I get the p-value doing an ANOVA test?
I want to regress two series (one big series divided in half) with the mean of the big series.
I do that because I would like to "investigate" the relationship between those two subseries and the ...
3
votes
2answers
621 views
General approach for non-parametric two-way ANOVA
Apologies for the almost text-book like question.
I have a 2x2 design with fixed categories and a continuous response variable.
If the variances are equal between groups (Bartlett test) and ...
2
votes
1answer
285 views
General linear hypothesis test statistic: equivalence of two expressions
Assume a general linear model $y = X \beta + \epsilon$ with observations in an $n$-vector $y$, a $(n \times p)$-design matrix $X$ of rank $p$ for $p$ parameters in a $p$-vector $\beta$. A general ...
3
votes
2answers
2k views
Difference between t-test and ANOVA in linear regression
I wonder what differences are between t-test and ANOVA in linear regression?
Is a t-test to test whether any one of the slopes and intercept has
mean zero, while ANOVA to test whether all slopes ...
3
votes
0answers
166 views
Weighted regression for categorical variables
I have been trying to use weighted regression on some data where there are three categorical variables with the
lm(y ~ A*B*C)
command in R.
This was to try ...
5
votes
1answer
621 views
Should the difference between control and treatment be modelled explicitly or implicitly?
Given the following experimental setup:
Multiple samples are taken from a subject and each sample is treated multiple ways (including a control treatment). What is mainly interesting is the ...
7
votes
1answer
541 views
What are some good hard exemplary problem sets to work through to solidify my understanding of statistical concepts?
Over the years, I picked up many Statistics Concepts in by a variety of situations and means. I studied some Statistics maybe for a couple semesters almost 10 years back. But I also picked up concepts ...
5
votes
4answers
824 views
Understanding multiple regression output
I am a first year psychology student. I am doing some research work with a prof, unfortunately the material that I need to use right now is covered only in my second year. But I need to already know ...
