# Questions tagged [intercept]

The intercept in regression-type models is the value of the Y variable when all X variables are 0.

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### What is the intercept in a regression model with demeaned dependent variable?

Suppose you have a regression model $\tilde{y}$ = $X\beta$ + $\varepsilon$, where $\tilde{y}$ = $y$ - $\bar{y}$ and $X$ contains a constant. If you estimate the model by OLS, does the estimated ...
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### All variables are not significant, but intercept is

I am using SPSS for the first time and just trying to make sense of my findings. I had two IV (nationality, age group), each with 2 levels (English-non English; young-old), which is why I ran a 2x2 ...
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### How to simulate data of a random intercept effect model in R?

I want to simulate data of the following random intercept effect model in R $$Y_{ij}=\alpha+\beta x_{ij}+u_{0,i}+\epsilon_{ij}$$ $$u_{0,i} \sim N(0,\tau^2)$$ $$\epsilon_{ij} \sim N(0,\sigma^2)$$ Here ...
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1 vote
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### Why model expected value is computed using a model with input features?

This post is kind of related to these two posts here and here I learnt that model expected value (average prediction) is nothing but performance of the model when all input features are absent. But I ...
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### Interpreting wgls output coefficients to construct equation of a line

I have the following model which looks at the relationship between number of boats (continuous) and frequency (factor) on recorded sound pressure level (continuous). ...
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### Is this intercept-free regression line really correct?

I know there are many arguments against intercept-free regression but we are very interested in the convex or concave shape of these lines. Because I got suspicious real results, I switched my ...
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### Chisq test for significance of intercept in R

I have a logistic mixed-effects model with both fixed and random effects. Imagine something like: ...
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1 vote
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### Multiple Regression, R output how to interpret the intercept

In the example linear regression below, how do I interpret the (Intercept) with this R output? A) Does the (Intercept) line represent pop1? B) Does the Estimate column indicate the slope or the ...
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### Logistic Regression, ''Intercept'' instead of a Category [duplicate]

I am currently trying to analyse the effect of an ilness (0= no infection, 1= infection) on 9 different Genotypes in plants. My Dataframe consist of 2 colums Genotyp and Infection. I have 459 rows for ...
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### Understanding fixef() output of fixed effects coefficients

I have a panel data set with several ID's and each has a certain number of year observations. When I fit a fixed effects ...
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### When you are running an analysis with only an intercept, does it make sense to include random subject and item intercepts?

Lets image a study where people get two shapes and are told to pick one. They each get 40 trials, each with a different shape/colour. There are 40 different pairs of shapes. There are 100 participants....
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### Is computing the average of a ratio the correct approach, and how to do it with nested data?

In general, is computing the average of a ratio appropriate? And secondly, is the nested model below appropriate for doing this? Here is a data set created from the Iris data that resembles my ...
1 vote
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### How to decide if I should fit SARIMAx with or without intercept

I am trying to find the best SARIMAX model for my data, I am using auto_arima to find the order(ARMA and Seasonal) of the model. How do I decide whether or not I ...
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### Compare intercept of logistics (mixed-effects) model to value other than 0

Is it possible to compare the intercept of a logistic mixed-effects model to a value other than 0? Specifically, I have two choice alternatives and try to predict choices. My intercept would then tell ...
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### How to calculate the intercept (b) of a gaussian kernel support vector regression

I know the dual problem of an SVR problem is given as: where \alpha_i and \alpha^*_i are dual variables and they are also decision variables in the above problem. \epsilon specifies the epsilon-tube ...
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### If I consider the fixed factor as a random slope, the p-value changes from p<0,05 to p>0,05

I'm having a hard time trying to understand the differences between these two models and why the first one shows correlation (p-value < 0,05) but the other one doesn´t (p-value > 0,05). I would ...
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1 vote
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### Consistency of OLS when no intercept

Suppose I have a model $y_i = \beta_0 + \beta_1 x_i + e_i$ but instead I estimate $y_i = \beta_1 x_i + u_i$ using OLS. That is, I ignore the intercept. Working out the algebra, based on this post, we ...
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### What is the difference (if any) when talking about bias from a ML point of view and from a DL point of view

I'm reading around Machine Learning and Deep Learning and can't seem to understand the difference or similarity between bias in both. If we look at the simplest linear regression formula y = b0 + b1x1 ...
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### Different values for intercept estimate in linear regression

I'm reading about linear regression from two sources. In here: https://online.stat.psu.edu/stat415/lesson/7/7.3 the estimate for the intercept is just $\bar y$. However over here: https://www....
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### Collinearity between the intercept and (logged) continuous variable: centering to fix it?

I have found a lot of information when there is collinearity between intercept and dummy variables. However, my collinearity diagnostics is showing a condition index > 30 (36) and it indicates ...
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### Why is the intercept different in an AR(1) model compared to a lagged endogenous variable model? [closed]

In other words, why is that when estimating in EViews y = c ar(1) yields a different coefficient for c when compared to ...
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### Simple linear regression without intercept - Expected Value and Variance Estimator (Slope) [duplicate]

I'm solving an exercise while studying for exam, I have been asked to find the estimator of simple linear model without intercept estimator, its expected value and variance. I got for the Estimator B1 ...
1 vote
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### Mixed model fails to converge - do I delete the random intercept or the random slope, and what does the variance of the random effects say?

I'm in the process of building my mixed models, and unfortunately I encountered a problem when creating the random effects structure. I have two random effects: ResponseId (i.e., participant number) ...
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### Interpreting constant in regression with an interaction term

In a regression model with a single categorical exposure and no interaction term of the form: $y = \beta_0+\beta_1x_1$ the $\beta_0$ can be interpreted as the result in the reference group. So for a ...
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### In R there is a problem of intercept and without intercept ,Pearson's Correlation does not follow! Why? (see the bolded resuls)

Xvec <- rnorm(200) Yvec <- 2.6*Xvec + rnorm(200) lmodxy <- lm(Xvec ~ Yvec) lmodyx <- lm(Yvec ~ Xvec) summary(lmodxy) Output ...
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### How to correctly use I-Splines for monotone non-decreasing/ increasing regression?

I have the following data to which I want to fit a monotone non-decreasing spline. ...
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### Test for comparing x-intercepts of two linear regression

I would like to know how to compare, and then calculate significant differences, if any, between the x-intercepts of two regression lines. Practially, I shoud compare the values of x when y=0. I know ...
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### Uncovering the make up of the intercept in a generalized linear mixed model

I could use some help Finding the make up of the intercept in a generalized linear mixed model. FYI, I use a 2013 Macbook Pro with a 2.4 GHz dual-core intel chip, 8 GB of ram, macOS big sur 11.2.2, ...
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