Questions tagged [biostatistics]
The science of statistics applied to the analysis of biological or medical data.
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Differences among Cox regression, accelerated failure time regression and linear regression when using no censoring data
I would like to investigate whether social economic status (SES) would be associated with the age of onset of mental illness, after controlling some possible confounders, in the cohort of patients ...
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Are mean, minimum or maximum temperatures the same in epidemiology?
I would think temperature, minimum, mean, and maximum temperatures the same thing.
I analyzed the effect of weather variables (daily mean minimum temperature, daily mean minimum relative humidity) on ...
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normality testing [duplicate]
Good day,
I am a medical student currently working on a thesis focused on metabolic syndrome. My sample size is 45 individuals. I have encountered multiple challenges in assessing the normality of my ...
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Why is density function of survival time called instantaneous failure rate
Why density function of survival time is called instantaneous failure rate. I am confused why density function is a failure rate for survival time.
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Chi-squared test with more than two variables, or should I run a different test?
I am looking at whether certain animals or categories of animals are more likely to use human-made trails than natural trails. We used camera traps and recorded for every case which animal it was, ...
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Is it possible to find a correlation coefficient in this situation?
I am new to statistics. I have a list of coyote sightings and am trying to figure out if the moon illumination percentage on that particular night is correlated to the sighting. Meaning, if the moon ...
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How to construct confidence interval out of a sample with small number of events?
I'm analyzing the results from an epidemiological study, where I have a sample of 2k persons with their respective ages and whether they were detected with a disease or not by different technologies. ...
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Assistance in sample size calculation using paired-t test
I am performing a prospective interventional study that is one arm. I need to calculate the sample size.
The study is about the impact of a specific intervention on systolic blood pressure. No studies ...
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Hierarchical partitioning for GAM model?
I am fitting a gam model with multiple environmental factors as predictors (actual evapotranspiration, climate water deficit, wind speed, etc).
My goal is to understand how each one of them contribute ...
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How to test for significant differences among percent increases between two unbalanced samples from each of 10 treatments?
I am trying to figure out how best to analyse fruit weight data from an experiment involving samples of both open-pollinated and unpollinated fruit from each of 10 different pollination treatments.
I ...
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Adding a categorical variable to a model fit for comparing parameter estimates?
I am fitting a non-linear model to multiples species where the y is growth rate and x is irradiance. These growth-irradiance curves are common and there is a great r package 'phytotools' that ...
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Multilevel multiple imputation in practice using R
I'm currently involved in a project where I want to address missing data using multiple imputation. I'm using healthcare data in a longitudinal setting with 16 time points, where observations are ...
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Is it possible to add a regression/fitted line equation to a mixed-effect model plot?
I have been asked to add a regression/fitted line equation to a negative binomial mixed effect model plot. Example of a regression line equation is highlighted in yellow below for ...
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Are pairwise ANOSIMs the correct post hoc test for an ANOSIM test?
I am comparing communities of insects between three different land use types (n=4 sites for each). I made an NMDS plot and all the groups looked very separate from each other (especially greenbelt ...
Yoyo
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Is it possibe to extrapolate abundance estimates of N-mixture models to unsampled parts of a species range?
I have repeated count data for a part of the range of the species I am interested in, and have used unmarked to get an abundance estimate for these. My understanding is that the population estimate ...
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Linear modeling of pseudobulk: how to model multiple types, conditions, and timepoints
I have pseudobulk gene expression counts from multiple celltypes that I want to perform differential expression testing on. The study includes a treatment, a pre and post treatment timepoint, and ...
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Why integrate out the random effect instead of jointly estimating all model parameters?
For simplicity, say I have a model with one random effect:
Y ~ N(XB + Zu, sigma), u ~ N(0, sigma')
So the likelihood function to ...
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Power analysis for cox-ph model for 8 (correlated) groups?
I am investigating covariate X for 8 cancer types which all have different survival rates and will possibly show different impacts of other covariates like age, sex etc. Therefore I will run 8 ...
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overall (allfit) and incremental cumulative association (cumfit) - R Package 'dlnm'
I am conducting research on the impact of between radiation dose and incidence of cancer in radiation epidemiology. To further explore this topic, I would like to utilize distributed lag non-linear ...
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When is "controlling for" effects nonsensical?
I am not as knowledgeable about statistics as I would like and I am looking for resources to help me understand what kinds of questions are meaningful and which are nonsensical. We are developing some ...
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Permanova with nested random effects?
I have an experimental design that looks like this:
Animals were reared from nine different source families and were placed in groups of 20 individuals into 18 rearing boxes (two boxes for each source ...
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How to compare Observed vs Predicted Outcomes for a Binary Dependent Variable
I have created a binary Logistic Regression model to predict if patients in a particular state, will die based on 10 or so predictors (demographics, income, physiological values, etc.) My dependent ...
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Multiple treatment group comparisons in a Generative Additive Mixed Model
I've fitted a GAMM using the mgcv package in R to some time course data from a biological experiment, with multiple drug treatment groups and a vehicle control ...
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How to estimate the baseline cumulative hazard function with ties?
I know that in the proportional hazard model, Breslow estimator is used for estimating baseline cumulative hazard. But what about when the data has some(or many) ties?
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Comparing Proportions of Different Measures within Same Data
I currently have 200 observations from different (randomly sampled) participants. For each participant, I have 4 measures: MS1, MS2, MS3, MS4. Each measure is a different binary measure for a ...
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Literature recommendation how statistics is used to make age/size/population/... estimates in biology
I was always interested how statistics is used to estimate e.g.
Weight of an animal from its foot size
Age of a shark from some measurements in its eyes
Age of a tree
Approximate population of some ...
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Scaling variables for model selection. Unscaling for final model?
I struggle with the following question:
I had to scale variables for model selection as they were in very different units and the model struggled to converge. Now that I have a final model the ...
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How to determine the best cut-off of measurement numbers for diagnostic decision?
I am currently doing a research on determining a cut-off of a ECG signal's number of 12 patients with their diseased/normal label that is produced by classifier for diagnostic decision purpose. ...
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How can I test significance of 2 PCA results/PCA polygons
The story so far is that I am comparing the climate niche of wild native UK tree species, with the climate niche of commercial growers that grow that species in the UK. Using the species code 'agl' as ...
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Mixed models for neonatal outcomes with twins
I am trying to fit a linear mixed model for a randomised controlled trial where women are randomised to one of two treatments, but the outcomes are at the baby level. Most women will give birth to ...
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Can Ordinal data have a difference in mean if one is comparing the same group at different points in time?
I'm currently looking at a study where Ordinal scales are used to compare the effects of drugs on Alzheimer at different time points throughout treatment https://www.ncbi.nlm.nih.gov/pmc/articles/...
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How to Determine the Number of Independent Tests When Considering Multiple Testing
I have a question regarding how to determine the number of independent tests when performing multiple testing corrections.
Suppose my research hypothesis is whether age is related to cognition decline ...
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Minuscule data for classification problem
I am working on a frog classification problem where I have 15 unique species and 2 recordings per species. Would it be a valid experiment if I were to have my training set of the 15 unique species ...
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How to account for predictors of different lengths or uneven distribution in GLMs?
I have different lengths/distribution for three predictors: year, location and cultivar. I ...
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How to interpret GLM without intercept?
I have a question about the output of my glm model WITHOUT an intercept. I am comparing the number of infected leaves on plants in different months. In the case of a model WITH an intercept (using the ...
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Would a GAMMA or Negative Binomial Generalized Linear Model be the right test for my data?
I want to compare the Perkins Eye Index (PEI) values, a measure of lobster egg development, between the months of January to June 2023. This is because I want to test the hypothesis that PEI varies ...
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In fitting a linear mixed model, can the output be used to test the significance between my groups after taking into account the random effects?
Background for the data:
I have two continuous variables "AGD" and "Weight", a categorical variable with 7 levels "Litter size" and another categorical variable "...
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Odds Ratio or 2 Prop Z Test
We would like to conduct an AB Test between 2 groups of people and the apps that people have to see which ones over or underindex.
Which is more appropriate odds ratio or 2 proportional z test and why?...
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Can I use log10(time) as an offset in a GLMM?
I'm trying to analyze a dataset but am running into a problem with one of my models. The particular set of data I'm working with is species richness data (number of species seen during each sampling ...
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Mixed model development for repeated measures over 3 years
I have longitudinal data for multiple plant varieties, where plants were measured for their Performance at 10 time points (time) each year for 3 years.
Each variety (genotype) serves as a distinct ...
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What distribution to use for continuous left skewed dependent variable in generalized linear mixed models? [duplicate]
I conducted a study to compare the effectiveness of different fungicides in controlling a plant disease. I assessed disease severity as the response variable, which is measured on a 0-5 scale. A ...
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Cannot apply simple OLS model in the case of low resolution devices resulting in Fourier space convolution
There's a problem which often comes up within my field and doesn't seem to be approachable analytically. Any suggestions or direction towards the class of problems this falls under would be helpful.
...
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Can I compare Fixed effect regression with IV regression.?
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How can I analyze the causal effect of variable X on Y using cross-sectional data? I have employed IV regression, but now I want to test the effect of X on Y specifically for individuals belonging ...
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Survival Analysis model choice
I am trying to investigate the statistical difference between two groups in my population and exploring suitable survival models for analysis. Let me first outline the data I am working with to ...
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Optimize ranking of fertility for a population of bacteria
I have a population of N male bacteria and N female bacteria.
I can make them reproduce together, and this process may or may not succeed, but it is a costly process.
The goal is to assign a reliable ...
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Can Shannon-Wiener index be used for measuring temporal differences? [closed]
I understand the Shannon diversity index being used in spatial analysis when comparing multiple sites of measurement, but can it be used to measure abundances, richness, diversity, etc. on a temporal ...
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Does this design indeed raise concerns about pseudoreplication?
We want to test the effect of dietary supplement on two groups of cows (randomized and controlled for starting weight and age). Group 1 (6 cattle) receives supplement 1 and group 2 (6 cattle) receives ...
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Kruskal-Wallis as a non-parametric alternative to 2-way ANOVA?
I'm a master student currently working with taxonomy and cultivation of wild edible mushrooms. In my experiment, I'm evaluating the effect of 4 distinct solid culture media and 4 temperatures on the ...
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Is Tweedie distribution appropriate for right skewed, continuous, positive response variable with many zeros?
I have a continuous response variable representing plant disease severity, with values ranging from 0 to 5. The R unique function shows the following values in my ...
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How to find overall data trends from count data across multiple subjects
I'm working with a dataset on ecosystem invasion, where individuals of an invasive species are "colonizing" a specific species of tree, tracked over time. Count data were collected 4-6 times ...
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