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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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18 views

How to test for significant differences between growth curves in repeated measures mixed-models?

I am comparing growth of fish in different habitats and since length and age data is derived from repeated measurements (back-calculations) I am using a mixed model (R, nlme). I have data from ~50 ...
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29 views

is LGM without factor variance just comparing means?

Let’s say a simple latent growth model with just two time points, constrained the variance of these two time points to be zero. Are the latent intercept and latent slope then merely using the mean ...
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Can formative measures contribute to latent slope/intercept through a MIMIC model?

I am interested in examining the global trajectory of V over 3 time points (as shown in the figure). Latent V is specified by 4 indicators and 4 predictors/formative indicators. We fixed the ...
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ML method to determine growth of accounts in a bank

Assume a bank has today N checking accounts, and also has 10 years history of the account balances. The history also includes related features such as "Allow overdraft" (Yes/No) and "Opening branch" (...
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Testing for Interaction terms nested models

I have a growth curve model to explore the main factors affecting reading progress. I added gender, income deprivation affecting children index and English as an Additional language as the main ...
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1answer
40 views

Estimating common slope across two traits for a parallel growth curve model

I am using a parallel growth curve model with 5 waves longitudinal data to evaluate correlated change among 2 traits. For models that showed the effects of correlated change among traits, I'm ...
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1answer
77 views

Modeling growth curves with different starting sizes (NLME in R)

I am trying to model fish egg growth over time given a starting egg size in R. I have repeated-measures data from individuals with grouping variable "Zafra.1". I do not know when the eggs started ...
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21 views

hierarchical linear modeling (HLM)

We are running longitudinal growth curve model in order to predict change over time. Each participant could provide up to 9 measurements (at a variable interval), and we would like to calculate the ...
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1answer
101 views

How to calculate growth rate from a semi-log plot?

In the following plot, if we model the population growth as a linear function of time, what would be a good estimate of the linear growth rate? I don't know if it's the slope or the intercept!
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45 views

How do you choose an appropriate time series regression model?

I am working on a research proposal where I want to test the effect of different macroeconomic variables (i.e. government spending, FDI, trade openness, international GDP growth, etc.) on the GDP ...
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1answer
39 views

Dealing with different units and indexes in regressions

In my time series model, my dependent variable is a growth measure in percentage. However, one of my independent variables is an index that ranges from -2.5 to 2.5 - and is producing some extreme ...
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What type of transformation for Latent Growth Curve analysis with lavaan when observed variances are over 40,000,000?

Edit: I believe a linear transformation is just fine - divide each number by 100 for example. Just make sure you change back your units when you are interpreting the output! In fact, when I do this, ...
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40 views

Change in X Predicts Change in Y

I have a fairly small sample (about 50 individuals) measured at three points in time. At each time point, I measure an outcome (Y) and a possible influence on that outcome (X) along with some ...
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34 views

Path analysis of latent variable relationships over time for hypothesis testing

Consider that I have a sample of 30 people (my real data are much bigger), and we ask them how often the would like to eat three types of food (candy, vegetables, and meat) at four points in their ...
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29 views

What test to use to compare within-group over time?

I have a set of data of $\approx 13$ people. We collect their data every 2 months for 2 years. I'm interested to see if a variable A in the data affect people's performance as well as their growth ...
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How to quantify SKU growth by removing the effect of price?

I am having Price ($/litre) and volume (litres) sold information at a Brand and also at a SKU level by weeks. I am looking to find out the SKU brand trajectory/growth by removing the effect of price. ...
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1answer
58 views

What statistical model to use for assessing the effect of a new tree pesticide?

I have 2 sites with 15 trees on each site. I plan to treat all 15 trees in site 1 with a new pesticide and leave all 15 trees in site 2 untreated. The total number of bugs on each tree is measured ...
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63 views

Modeling a repeated measures growth curve

I have cumulative population totals data for the end of each month for two years (2016, 2017). I would like to combine these two years and treat each months cumulative total as a repeated measure (one ...
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1answer
96 views

Interpreting fixed effect time and cross-level interaction time in growth model (multilevel model)

In my dataset time is nested within person. I have done a multilevel analysis with time on the first level and subject on the second level. There is a significant fixed effect of time on the dependent ...
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254 views

Growth Curve Models using lmer() function in R (lme4 package)

I am interested in changes in depression surrounding different life events and if personality traits (level-2 predictors) affect these changes in depression. In a given longitudinal data set, each ...
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506 views

asym, xmid, scal biological interpretation for Self-Starting Nls Logistic Model

I built logistic models using self-starting nls logistic models using SSlogis and nls functions in the base 'stats' package in R. I had a couple questions about the biological interpretation of the ...
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424 views

How to report Likelihood Ratio as Chi2 / Δχ2 value

I'm comparing different models of a growth model using RStudio and the anova(model1, model2) command. I get an output like (values completely random, just as example): ...
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594 views

Mixed Effects model with quadratic term in fixed, but not in random part

Say one wishes - and believes - to fit a mixed effects model where time ($x_{ij}$ below) is included in a linear and quadratic term in the fixed part, but only linear in the random part (hence random ...
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1answer
60 views

Students nested in both middle and high schools over time - what to do?

I have a question about one of the papers I'm reviewing. The authors used a piecewise growth curve model to estimate trajectories of key variables before and after the middle to high school transition....
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1answer
707 views

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 ...
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662 views

How to compute number of dichotomies/growth function value?

I am studying the book 'learning from data' by Mostafa. I understand that the number of dichotomies for positive rays on the number line is $N+1$ (ie if you have one point, $x$, on the number line, ...
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108 views

Growth Mixture Models in MPlus

I'm new to mixture modeling and MPLUS, so apologies if this question is misguided. I am currently working through a dataset and learning off of Higher-Order Growth Curves and Mixture Modeling with ...
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32 views

Fitting a logarithmic growth curve with error (an interval) of the explanatory variable?

I have a series of human growth data that I wish to fit to a 3 parameter logarithmic growth curve: s(i) = Beta0 + B1*T + B2*ln(t), where s is a length and t is an age. The only problem is that this ...
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86 views

How to fit data with an interval-censored explanatory variable?

I have a series of human growth data that I wish to fit to a 3 parameter logarithmic growth curve: s(i) = Beta0 + B1*T + B2*ln(t), where s is a length and t is an age. The only problem is that ...
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1answer
109 views

log growth model

I'm trying specify an econometric growth model in a cross-section of 5000 municipalities (counties) observed at time $t=1990, 2000, 2010$. I want to see if there are some county characteristics that ...
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1answer
298 views

growth curve analysis - problems with model fit

I'm very new to GCA so sorry in advance if the question is very basic. I have run an eye-tracking experiment in which participants look either at one of the elements or the other (so I have a binomial ...
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1answer
72 views

Computing growth rates with drastically changing sample sizes

I'm computing growth rate for some companies annually for 3 years using this formula, for each year: ((# customers year 2 - # customers year 1) / # customers year 1) * 100 The problem I'm running ...
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2answers
105 views

Calculating implied values of a model

How are the implied values and their standard errors calculated here? Thank you in advance. http://imgur.com/a/3dMdx Edit We have this production function with $\alpha+\beta<1$. $Y=K^{\alpha}H^{...
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1answer
1k views

nls() gradient error in fitting growth curve data

I am trying to model the following data on promotional budget and customer awareness. The idea is, at some point, increase in budget doesn't have any further impact on awareness; it saturates. ...
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1answer
496 views

How to implement initial GDP variable in time-series growth regression?

I am running a regression on real GDP growth as the dependent variable. I am trying to include an initial year for GDP as an independent variable to control for the initial state of development in a ...
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1answer
33 views

Longitudinal design: Which method to use if the dependent variable was measured during fewer occasions than the predictors?

I have a longitudinal dataset with 8 repeated measurement occasion and approximately 100 cases. Some of the explanatory variables are time-variant, other stay the same over time. Some might be ...
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47 views

How to compare / evaluate parametric growth curves

So I fit a set of (nested) growth models (logistic, gompertz, richards, plus some variants, eg. https://en.wikipedia.org/wiki/Generalised_logistic_function ) to random sub-samples of my data to figure ...
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1answer
289 views

Latent Change Models: account for change in one latent variable as function of change in another

Hertzog and Dixon (2003) specify that latent change models make it possible to predict change in one latent variable based on change in another. I would appreciate help conceptualizing how to create ...
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30 views

No change over time. How to continue analysis?

I would like to conduct a growth curve analysis on longitudinal data. I have read that it is wise to begin with an unconditional means model first, and then move on to random intercepts, and random ...
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489 views

Comparing two growth curves (SPSS)

I conducted a study in which students filled out a questionnaire about their motivation at four different times during a semester. Motivation was split up in different types of motivation (as such, ...
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1answer
33 views

Adjust customer complaints volumes for growth in subscriber base

I have two sets of monthly data that spans over almost 2 years. The subscriber volume, and the customer complaint volume. I'm trying to determine the best way to adjust the changes in complaints ...
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195 views

GLM for relative growth rates

I have this experimental design: I have two sets of cell lines. One in which I mutated a gene and another in which I didn't and therefore serves as the control. I grow each of these cell lines under ...
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1answer
503 views

Are lower-order interactions a prequisite for three-way interactions in regression analysis? [duplicate]

I'm applying growth curve modelling and am interested in modelling a three-way interaction between predictors A x B x C. From what I remember a condition for modelling three-way interactions in ...
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296 views

Repeated Measures in SEM

I would have a question about using Structural Equation Modeling for comparing repeated measures results. I have a one DV which has been measured 4 times and corresponds to 4 different experimental ...
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1answer
379 views

paired t-test as a simple latent change score model

UPDATE: This problem was (embarrassingly) solved by specifying the intercept in the regression equation as shown below: ...
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1answer
726 views

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 ...
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2answers
3k views

How to normalize and compare growth rates between variables at different stages of some kind of growth model “curve”?

I have a data frame that has various capital and metropolitan cities with various economic, market and performance data. One set of variables is each total annual non-domestic visitor volume and the ...
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82 views

How to specify a significance test for intercept and slope between multiple latent groups

I have done a Latent Profile Analysis on 34 symptom-distress-items at beginning of psychotherapy treatment. I came up with 5 latent groups. The entropy of the model was 0.779 The average Latent ...
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41 views

statistical test in R for normalized time course data

gene time average stdev gene1 24h 1.1 0.01 gene1 48h 0.9 0.023 gene1 72h 0.7 0.01 gene1 96h 0.5 0.021 My data above ...
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How to use linear regression to model population growth?

I've been working on finding the regression line that will help make predictions on the future population. The data I have is from the past 20 years and every year there has been an increase, the data ...