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# Questions tagged [growth-model]

A growth model is a statistical model describing the growth of some population, be it in demographics, biology or otherwise. A well-known example is the logistic growth model.

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### Distribution to describe size of population with random exponential growth

Is there a distribution family that describes the size of a population experiencing random exponential growth (either discrete or continuous)? For context, I am trying to computationally model a ...
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### Can you use a binary outcome variable in a longitudinal latent-growth mediation model

I am wanting to create a LGCM in which I am assessing whether two latent factors (the intercept and slope) mediate the relationship between a continuous predictor and binary outcome variable but am ...
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### The difference between conditional and unconditional models when developing a longitudinal mediation latent growth curve analysis

I was just wondering if anyone could advise me on what the definition of an unconditional and conditional model when you are taking a stepwise approach to developing a mediational latent growth curve ...
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### Standardized or unstandardized coefficients to report? The covariances and regression of a multivariate latent growth model

I am currently running a second-order latent growth curve with multiple constructs. This multivariate latent growth curve demonstrates how two (or more) constructs travel together across time. My ...
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### How to analyze between-group differences in within-group variances over time in a 3-level model?

The data I am using is collected within the physical fitness surveillance program in schools. In these schools, either no intervention, healthy lifestyle intervention, healthy schools network ...
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### Dry skull vs live skull measurement adjustments

I am working on a dataset that has dry skull measurements from a museum's collection (twice as many samples) or a live specimen (less common). As you can imagine, the live specimen are on average a ...
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### Converting quarterly growth rate forecasts to yearly growth rate forecasts

I'm generating forecasts on a quarterly basis, focusing on metrics like the GDP growth rate for Brazil. These forecasts are presented as growth rates. For example, the forecast for 2020Q1 represents ...
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### How to analyze time varying covariate random effect

I am running a multilevel growth curve model to examine predictors of social anhedonia (SA) trajectory through ages 12, 15 and 18. SA is a continuous numeric variable. The age variable (Index1) has ...
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### Different time trends of groups: quadratic vs. linear decline

Suppose we have two groups of individuals A and B that we observe over time on a parameter, say blood pressure. We want to compare the group effect over time in a GLMM using ...
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### Reporting results for time-invariant predictors in latent growth curve models

I am results for reporting a time invariant predictor of the intercept and slope factors within a latent growth model, adjusted for covariates such as age and sex. My dependent variables and ...
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### How do I interpret a second-order multi-variate growth model?

I am running a multi-variate second order growth model. I have two factors, which are conceptually related to each other measured on 7 different occasions. Wanting to know how the two factors ...
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### How to code for a mulitgroup analysis concerning two catagorical variables

I have a question on syntax for Mplus. I am running a multivariate latent growth curve with 7 repeated measures, variables X and Y (diagram attached). I also have two grouping variables, sex and ...
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### Growth Curve Model with time-invariant covariates- standardized CIs

I ran a growth curve model (GCM) with covariates and used the 95% bootstrapping CIs to interpret the effects of the covariates on the intercept and slopes. I noticed that the upper bound of the CI of ...
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### Bad model fit for a second-order growth curve with time-varying covariates. Do I have to find a way out or will it depend on the aim of the analysis?

I am running a second-order latent growth curve model with seven repeated measures. I have 2 time-invariant covariates (TIC, country and sex) and 2 time-varying covariates (TVC, both are latent ...
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### Is there a way to make a latent class a predictor of a latent growth model?

I was wondering if it is possible to run a second-order latent growth model, where latent classes can be added as a covariate? I have three variables of which I have 7 repeated measures, say, variable ...
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### Obtain one single growth curve from various replicates in a growth experiment

I am performing a yeast growth experiment measuring areas of growth across a time interval, therefore having area (%) as my dependent variable and time (min) as my independent variable. I have three ...
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### Why Adjusted R^2 falls if I include both individual and time fixed effects?

I have a (probably simple) question on fixed effects estimation. I am trying to do baseline growth regressions of log GDP per capita against a number of covariates and, in line with the literature, I ...
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### p values of latent basis models

I am running a latent basis model and wondering if anyone could provide insight on how to interpret the p-values of the basis coefficients. The basis coefficients are set to 0 at T1 and 1 at T9 and ...
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### Do scale applying approaches need to be the same for longitudinal invariance testing and the subsequent growth curve model?

I have a question concerning scaling approaches in longitudinal invariance testing and a subsequent latent growth curve. That is, for example, if the invariance test was conducted with a marker ...
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### Growth Mixture Model/Latent Class Growth Analysis for binary/binomial outcome in R?

Latent Class Growth Analysis and Growth Mixture Models (synonyous; henceforth referred to as GMM) explain between-subject heterogeneity in growth on an outcome by identifying latent classes with ...
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### Do you need to correlate factor residuals of factors that are measured at the same time point

I am running a second-order (multiple indicator) latent growth curve. The model has three latent factors (excluding the growth intercept and slope factors) that each have 4-5 indicators. Two of them ...
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### How to Estimate Growth Rates Between Two Periods from Data with Varying Time Intervals Between Measurements?

I have a dataset of sales records for properties in a local area spanning over 20 years. Each property has one or more historical records of sale, however, as the sales do not occur every year, there ...
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### What possible effects to include when running a Mixed Model, time variable and or lags for DV's and IV's?

I'm doing analyses in R on 5 repeated observations over a period of 5 years (repeated/random dv: 'amount of professional health care', repeated/random IV's: 'amount of social support' with several ...
3 votes
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### How can I calculate the required sample size for Latent Growth Curve Modelling?

I am looking to calculate what sample size I would need for my study by running an a priori power analysis. Is there any way (e.g an R package) I can calculate the required sample size required for ...
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### Interpertation of a conditional quadratic latent growth curve model (i.e., with predictors)

I have a conditional quadratic latent growth curve model and am wondering how to interpret the results. My predictor of interest is significantly associated with the slope factor (B = -0.45, p = .001) ...
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### Latent growth curve model: should you include predictors if the variance for slope and/or intercept factor is not significant?

Hi I am running a series of latent growth curve models. I am wondering: can predictors of the slope and intercept factor(s) be included when the slope and/or intercept variance are not significant, or ...
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### Latent growth curve model: The variance-covariance matrix of the estimated parameters (vcov) does not appear to be positive definite

I have run a latent growth curve model in R using lavaan and got the below warning. It would be good to hear suggestions on how to resolve this warning. The full output is below. Note that I dummy-...
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### Latent growth curve model with a continuous time-invariant covariate, multi-group or covariate model?

A Latent growth curve model with a time-invariant covariant can be specified with (at least) two ways, by using the multigroup model approach or the "regression approach". By regression ...
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### Effect of robust maximum likelihood estimator in structural equation modelling when data is normal?

I understand that when data are nonnormal robust maximum likelihood estimator can be used. I'm wondering are there any disadvantages of using a robust maximum likelihood estimator when the data are ...
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### Structural equation modeling (latent growth models): robust estimators to handle outliers?

Can I use robust estimators (e.g., "MLM" and "MLR"estimator lavaan options) to overcome outliers within my sample, or should I remove outliers? For context, I am modelling the ...
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### Lavaan growth model: to treat endogenous variable as ordinal or continuous

I am modelling the trajectories of scores on two cognitive tests (i.e., PAL and SOS) measured at four time points. To do this I am creating separate latent growth curve models for each cognitive test, ...
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### Growth mixture model (hlme) from lcmm R package failing to converge - continuous timepoints?

I am currently creating a naive model, where the outcome is a continuous biological variable, and the time to measurement is a continuous time variable, defined as the time since the individual ...
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### How to improve sample representativeness for longitudinal data collected via an online platform?

I am working with a longitudinal dataset exploring cognitive ageing (e.g., memory performance over time). Participants complete the study annually. Inclusion criteria for this study are 1) UK resident,...
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### How does a latent variable's communality value (R-squared) afect the interpretation of a latent basis model?

I am running a latent basis model with 5 time points. The model has 5 measures of 5 items that make a factor. I ran the model with the folloing code(Mplus) ; ...
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### Singular gradient errors in nls in R studio [closed]

I make fisheries work, and I need to estimate some parameters from the von Bertalanffy equation: Lt=Linf*(1-exp-K(t-t0)) here Linf, K, and t0 are the parameters that I want to estimate by FSA package ...
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### Latent growth curve model - can I talk about an effect over time if I only have my outcome at the last timepoint?

I have a latent growth curve model with two variables. X (exposure to media) was measured at 5 time points over several years. Y (misinformation proneness) was measured only at the last time point (...
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### How to interpret results of a latent basis analysis when the estimated lambda exceeds 1?

I have ran a latent basis analysis and got the results below. S BY AE1 0.000 0.000 999.000 999.000 AE2 0.714 0.185 3.867 0.000 AE3 ...
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### Consequences for not estimating autocorrelated residuals in a growth curve model

I am fitting a second order growth model with 7 time points on Mplus. When I estimate the model with autocorrelated residuals in it the model will not run because of identification issues. (when I ...
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### Compare latent trajectories of two groups based on same model using SEM

I fit latent growth models using lavaan's growth() function in R. It looks like this: ...
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### What statistical analyses would you use to analyze the change across two time points, months apart?

I will be administering an early literacy assessment to preschoolers at 2 time points in the preschool year. I want to be able to examine the growth from point A to point B. I also wanted to ...
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### Regressing slope on intercept in multivariate growth curve model

I'm running a multivariate growth model with two variables measured across 3 waves using lavaan/growth function. Here's the model specification I'm using, with non-uniform time differences. Two ...
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### fitting growth curves with nls singular gradient error [duplicate]

I'm having trouble fitting my model to a bacteria growth curve. I made a sample of my data below. Code: ...
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### Which method to use to scale/mean center a time-varying covariate in latent growth models (SEM)?

I have longitudinal data across several time points. At each time point, participants completed an online test up to 3 times (i.e., measurements were completed 1-3 times at each timepoint). The number ...
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### Who formulated this Generalized Lotka-Volterra model? [closed]

In the introduction of this paper Bifurcations in a predator–prey model with general logistic growth and exponential fading memory The authors claim I didn't know that this model was well known. Can ...
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### Phonological errors in children

I have a data (ge3_ratio) with 86 observations measuring the ratio of phonological errors produced by children. The data was collected from spontaneous speech transcripts from 3 children aged 21 to 65 ...
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3 answers
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### nls() singular gradient matrix at initial parameter estimates error

I am trying to run a nls() to interpolate height growth of a tree given a series of samples, where each sample has a value of age, and height. I am using the Richards (1959) method:  \textrm{Height}=...
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### What method should I use to study population level growth and individual level growth?

I have a panel dataset which contains diameter measurement data for 88 trees obtained from a mapped stand in Duke Forest. The description of variables is: Each tree is indexed by a unique ID (ID), and ...
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### Latent growth model - Is it possible to fit this model on latent variables?

Would it be possible to fit latent growth curve model on latent variables instead of directly on the observed measures? Each latent variable would represent a latent construct (e.g., intelligence) at ...
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### Fit Gompertz curve to growth data with decline phase

I measured the change in three traits (y1, y2, y3) over time (x). The three traits each reached a maximum at different times and then declined. I am interested in the phase until the max and would ...
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### Power analysis and sample size for multilevel modeling growth curve (repeated measures)

I am aware that there are some useful threads already on free software for calculating sample sizes (see here). However I couldn't find anything specific to cross-classified MLM and repeated measures. ...
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