# Questions tagged [dose-response]

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### How is this formula derived

I have carried out an experiment with several repeats and my program has returned the values of EC50 and its CI(95%) confidence intervals, LogEC50 and the standard error of (LogEC50). The logs are ...
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1 vote
97 views

### Example in which $E[E[Y|T,X]] \neq E[Y|T, E[X]]$

Context: this question is a follow-up of this other question in which I'm trying to understand why we should use methods for causal inference instead of just training machine learning regressors, ...
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1 vote
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### When does Dose Response Function estimation work better than simple regression?

I have been recently asked what is the difference between a Dose Response Function (DRF) estimation (as the one proposed in this link and this paper) and a statistical regression method. I therefore ...
• 460
1 vote
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### Fitting Log Logistic 4 parameter Mixed Model

I have a set of experimental growth data where I exposed a group of animals to increasing concentrations of multiple toxicants. Two toxicants were run at a time in batches due to material ...
76 views

### Comparing Multi-level Meta-regression to Network Meta-Analysis for Dose-response Project

I am planning a meta-analysis to examine the average change in a continuous variable over time within my area of research. To be able to meta-analyze this continuous relationship, I've typically ...
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1 vote
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### balanced and unbalanced dose response experiments

Consider a dose response study where there are four active treatments (from the highest dose and lowest dose) and also a control. One goal is to test the hypothesis that treatments are more effective ...
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### How to calculate MEC90 or MEC95 with isotonic regression in R?

Several studies calculate the minimum effective concentration (MEC), volume (MEV), or dose (MED) as MEC90 or MEC95 and base the calculation on a study by Pace and Stylianou. One of the best ...
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1 vote
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### Biphasic dose-response: what model to use in R drc() package?

I am trying to model a dose response curve that has two phases (i.e. two steps). GraphPad Prism has the model in their workflow, but I am trying to accomplish the model fitting in R. With the ...
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### Functional analysis in R with fda

I'm working with time series data for drug response. And, I wanted to as is there are some alternative ways to analyse it since the FDA package in R is not working in my case. The type of my data is ...
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### Cox model: advice on constructing time varying exposure to drugs

I am performing a survival analysis on medical registry data and would like to model drug exposure to estimate a continuous dose-response curve. I have drug data like this: where ATC is the unqiue ...
• 859
1 vote
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### Error propagation in normalized data to be used for non-linear modeling

I have been given data where the raw readings conventionally have the mean of "blanks" subtracted from every reading. Then the blank-subtracted readings are divided by the mean blank-...
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### ED50 in non linear logistic regression in R

I am new to R and I want to find the ED50 with its confidence interval in the drc package in R. I found the best model is lorentz.4 according to AIC. But I get a warning message for the confidence ...
59 views

### Alternatives to ANOVA for kill assay

I'm trying to find an appropriate test to compare my data. I ran a 2-way repeated measures ANOVA to compare different drug concentrations' effects on bacterial population count at different time ...
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1 vote
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### Combining continuous outcomes in a meta-analysis using same individuals (doses, time periods/repeated measures, and behaviors)

In case anyone sees this in the future, this is what I did. For different concentrations, I did combine them. Specifically, what you do is combine the treatment groups and compare to the single ...
1 vote
45 views

### Problem fitting quadratic model in 'dosresmeta' package due to error regarding "leading minor"

I am trying to use the doresmeta package in R to evaluate the dose-response relationship between supplemental intake of a micronutrient and risk of a disease. When ...
320 views

### What assumptions need to be met for a hormesis model in R?

I conducted a toxicology study where I exposed fish to 6 concentrations of an effluent treatment for 10 days. At the end of the experiment, I measured 10 endpoints with the fish plasma to determine ...
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### How to normalize mortality in determining lethal concentration of toxins or pesticides?

A certain set of pesticide concentrations is selected to dose the animals to determine its acute toxicity. Technically, with increasing concentrations, the mortality should increase, but that does not ...
1 vote
21 views

### Calculating doses using Continual Reassessment Method

Having trouble with this problem. Doesn't seem too difficult but can't find the easiest way to set up equations to solve it. We are given beta distribution toxicity level and starting dose. PROBLEM We ...
1 vote
70 views

### Power analysis for drug dose study

I am proposing a study that tests dosages of X drug as a treatment for Z disease. Basically the participant will take a starting dose of say 10mg and every two weeks the dose is upped by 10mg. The ...
69 views

### Statistical analysis for a randomized controlled trial where dose is possibly changed during every measurement?

Suppose you're conducting an RCT to assess the efficacy of a medicine. You recruit, say, two groups and you plan to measure a primary outcome at baseline and at two and four weeks follow-up. You also ...
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### Drug Efficacy - Probability Plot for Sputnik V

On the Wikipedia page of Sputnik V vaccine, results of Phase III study are reported, where the drug efficacy is visualized for the first and the second vaccination (attached picture). Does this plot ...
1 vote
123 views

### How should I interpret the results of linear and non-linear dose-response meta-analysis?

Fellow statisticians! I am currently doing a project involving dose-response meta-analysis, and I would like to ask how should I interpret my findings. I have estimated the linear dose-response effect ...
90 views

### Can you perform dose-response meta-analysis with only two studies?

Currently, I am conducting a meta-analysis on the association between BMI and prognosis. I discovered that the studies used various cut-offs. However, only two studies are eligible for dose-response ...
289 views

### Calculate LC50 from a non-sigmoid dose response curve

Is it possible to calculate LC50 (concentration that is lethal for 50% of the test organisms), when my dataset does not have a sigmoid dose response curve? For my experiment, I had 6 treatments ...
295 views

### Confidence intervals of percentiles in non-linear regression

I'm fitting a log-logistic model, $Y=1/\left(1+10^{((\log10(a)-\log10 (X))/b)}\right),$ to toxicity data ($X$ are concentrations and $Y$ are mortalities) using SPSS and Graphpad Prism. I get the ...
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### How is the Williams test in R related to glht with mcp set to Williams?

My objective is simple: to find the minimum effective dose. I want to use the Williams procedure, to say from which it starts. It seems there are different approaches, 1) contrasts method via glht, ...
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47 views

### Inference on the minimizing/maximizing value of $x$ in a regression

I have 30 pairs of observations $(x_i, y_i)$ and hypothesize that in the observed range of $x$ a non-monotone relationship $y_i = f(x_i) + \epsilon$ may hold. I am willing to assume that \$\text{Var}(\...
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### LC50 change in units and confidence limits [duplicate]

I performed a dose-response experiment and I have estimated the LC50 and a confidence interval. I've been asked to provide results expressed in several units (mg/kg and mg/L). I assume that I can ...
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### P for trend test in multivariate analysis

I'm trying to analyze dose-response using trend anlysis in SAS. In 2×2 table analysis, we can use Mantel-Haenszel test with proc freq. However, several study ...
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405 views

### The effect of a lack of dose-response results on odds ratio

This is part of a quantitative reasoning assignment I was working on. The study hypothesized that exercise may reduce the risk of disability for activities of daily living(ADL). However after ...
984 views

### How to estimate confidence intervals for LC50

This is my first question, so I hope the question is properly done (my apologies if it's not...) I am using a binomial GLM model (logit) for some toxicology data investigating the effects of a ...
74 views

### Inverted dose-response variables

Context: Often when we carry out dose-response modelling we want to estimate the dose required to elicit a predetermined response (i.e. response ~ dose). Typically this is done with inverse ...
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