Statistical Analysis Stack Exchange
Statistical Analysis Stack Exchange

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.

Wikipedia has an article https://en.wikipedia.org/wiki/Population_dynamics with further references.

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What are the differences between "Mixed Effects Modelling" and "Latent Growth Modelling"?

I'm decently familiar with mixed effects models (MEM), but a colleague recently asked me how it compares to latent growth models (LGM). I did a bit of googling, and it seems that LGM is a variant of structural equation modelling that is applied to…
Mike Lawrence
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Non-linear mixed effects regression in R

Surprisingly, I was unable to find an answer to the following question using Google: I have some biological data from several individuals that show a roughly sigmoid growth behaviour in time. Thus, I wish to model it using a standard logistic…
Rob Hall
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Best method to create growth charts

I have to create charts (similar to growth charts) for children of ages 5 to 15 years (only 5,6,7 etc; there are no fractional values like 2.6 years) for a health variable which is non-negative, continuous and in the range of 50-150 (with only a few…
rnso
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Instrumental variables and mixed/multilevel models

I want to estimate a growth model to model the growth trajectories of individuals $j$ over multiple time points $t$ by applying a standard mixed/mutilevel model (also known as random coefficient model): \begin{align} Y_{tj} &= \beta_{0_j} +…
majom
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Numerical properties of the logistic growth model for non-linear regression

I am using the nls procedure in R to fit a logistic growth model. In their SSlogis function, José Pinheiro and Douglas Bates chose the formulation Asym / (1 + exp((xmid-input) / scal)) for their model. As I am fairly inexperienced with the…
Rob Hall
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Plotting and presenting longitudinal data, options?

Hypothetical Scenario: A few continuous variables, each measured repeatedly at, say 12 time points, each with say, 150 observations. There are small fluctuations from one time point to another (i.e. change is not that smooth), but the variables are…
Sootica
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Confidence Intervals for the Parameters of a Logistic Growth Curve

I'm using the growthcurver library to estimate the parameters from some bacterial growth curves. It fits a logistic equation of the following form: This returns values for K, N0 and r in that equation, along with standard errors. I would like,…
Fomite
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Do logistic population growth models relate to binary logistic regressions?

I ask this because all resources regarding logistic regression in R involve binary outcomes, so they try to model questions like when will increase in temp cause a switch to fail (0, 1)—involving probabilities. But if we are talking about population…
hhhaaa1
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Demonstrate difference in growth over time

Short version Is there a difference per treatment given time and this dataset? Or if the difference we're trying to demonstrate is important, what's the best method we have for teasing this out? Long version Ok, sorry if a bit biology 101 but this…
dardisco
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Estimating growth rate from noisy data?

Let's say we want to estimate growth rate from noisy data. Due to noise, simple calculation will result in very poor estimates (calculating growth rates just exacerbates noise), so smoothing is needed. This is quite straightforward up to this point,…
Tamas Ferenci
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Updating/ adjusting theoretical growth curves when raw data becomes available

The research group I work for have developed a theoretical growth model for a particular species of fish. The idea is that if you provide some initial starting values for the model you then generate an expected growth curve along with 95% confidence…
user3136
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Change Score Model in lavaan

UPDATE: I think I was over-complicating my problem and am struggling through a new approach as described here: paired t-test as a simple latent change score model I am still accepting the answer below as it does appear the model is unidentified. If…
joemienko
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Growth models for a population

I'm studying the growth of a population (users of a website). I have the user count for each time block (which is 2 weeks long). Now, I'd like to understand if this growth follows a well-known growth curve. To start with, I ran this regression on R…
Mulone
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Baseline adjustment in growth models: Random Intercept or Baseline Covariate

Let's say I have outcome data at four time-points (baseline, 3 months, 6 months, 12 months) which I want to regress on an explicit time variable ($t_1 = 0$, $t_2 = 1$, $t_3 = 2$, $t_4 = 3$) to understand linear change. I typically adjust for…
PyjamaNinja
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How to calculate uncertainty in bacterial growth rates (or in the slope of any local regression)?

I'm using a plate reader to measure optical density of different bacterial strains so I can compare their responses (growth rates and changes in them over time) to stress conditions. The growth curves often don't follow any standard shape so I'm…
Jeff
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