Questions tagged [prevalence]

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How to deal with ragged power curve

I am exploring various methods for sample size calculation and power analysis from binomial data, and frequently coming up against ragged power curves that go up and down as sample size increases. I ...
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Learning Average Dependent 0/1 Variable

Suppose I have a matrix $X$ and a dependent vector $y$ whose entries are each in $\{0, 1\}$ dependent on the corresponding row of $X$ Given this dataset,I'd like to learn a model, so that given some ...
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4 votes
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Why exactly does a classifier need the same prevalence in the train and test sets?

Here are some commonly seen statements about the importance of prevalence in the train and test sets when developing a classifier: "Another reason not to rebalance datasets is that models should ...
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2 votes
1 answer
129 views

The percentile method

a research used the percentile method to find the prevalence in severe group as below: The outcome variable was categorized using percentiles to Mild, Moderate, and Severe in the Symptom Severity ...
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How can one control for FDR if we do not know the prevalence?

I am trying to understand the concept of FDR, and particularly "controlling" the FDR in multiple comparison testing. I undesratdn, and have used many times, the concept of α (type 1 error ...
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16 views

Post test probability with a ROC curve

I have data that is normally distributed related to risk of a particular disease. At the median of the distribution, you would expect to observe the population prevalence level of disease P0=0.01. For ...
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2 votes
1 answer
65 views

Should you include time as a continuous predictor when estimating incidence or prevalence?

Suppose one has a time series of disease counts and populations (at risk, total etc.) or, equivalently, binary events of disease status. Then suppose one wanted to present estimates of incidence or ...
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How do i perform a meta-analysis of prevalence rates using metafor package (with no treatment group)? [closed]

I have a spreadsheet with this type of information: ...
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15 views

How to determine probability of a test result given the FPR and prevalence?

Person A is predicted to have a disease that exists within the population once for every 1000. The prediction has a FPR of 10% (1 in every 10 false cases is incorrectly predicted as being positive). ...
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2 votes
1 answer
34 views

When comparing classifiers on different datasets with different prevalences, is it valid to calculate prevalence-adjusted PPV?

Scenario: comparison of 2 different binary classifiers Both classifiers report sensitivity and specificity and number actually positive (P), but classifier 1 is tested on a dataset with prevalence 20%,...
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2 votes
1 answer
26 views

prevalence ratio question

I understand that prevalence ratio is ...
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0 votes
1 answer
26 views

How to calculate NNT when it's NOT a clinical trial?

I am working on a revise and resubmit for a journal article. This is an observational, cross-sectional study. We compared endorsements of different behaviors across groups (e.g., 30.1% of Group 1 ...
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1 vote
1 answer
72 views

Prevalence/proportion estimates: sampling/screening steps in different order make a difference for SE of the estimate?

We have a question that is quite puzzling but that will surely be something others have come across (e.g., in epidemiology). There are two methods we are thinking of to get a prevalence estimate, the ...
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1 answer
22 views

How to treat proportions with different sample sizes as response variable in GLM / GLMM?

For an ecological research project, I am trying to model the effect of different factors on the prevalence of a specific pathogen in ticks. Ticks were collected from around 80 different plots and ...
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38 views

Testing the difference between 2 prevalence ratios

I want to test if prevalence ratio (a disease in Men vs Women) in population A is statistically different from population B. I wonder what statistical test can be used?
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1 answer
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Is there criteria on when to choose ODDS ratio or Prevalence Ratio?

Am stack between using Prevalence Ratio and ODDS Ratio. Is there any statistical backing on choosing one over the other? If yes, what could that be and would one generate the PR in R?
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1 vote
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Compare geographical distributions of prevalences

I would like to ask you what statistical method should be used to compare two prevalence distributions. My problem is the following: I have two prevalences of two diseases A and B (non-exclusive) per ...
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7 votes
3 answers
432 views

Are thresholds for logistic regression models prevalence-specific?

I wonder if thresholds for logistic regression models are prevalence-specific. I assume that they are, however, I am not sure about the basic statistical principles behind it and how to deal with the ...
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2 votes
1 answer
32 views

Is there any form or program that generates prevalence ratio values ​through logistic regression?

When performing a binomial or multinomial logistic regression, odds ratio (OR) values ​​are generated. Is there any form or program that generates a prevalence ratio value instead of OR?
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2 answers
22 views

Why do we measure incidence, if we can measure the prevalence of a disease for two successive years instead?

Why do we measure incidence, if we can measure the prevalence of a disease for two successive years and then subtract the latter year's figure from the former years number and find out the incidence? ...
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How to estimate prevalence with a zero incidence (rare disease)? [duplicate]

I had to solve the following problem. Newborn screening has been implemented for a very rare pathology. For 6 months, and out of 50,000 births observed, no sick case was observed. What is the ...
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1 vote
1 answer
44 views

How does a small sample size (underpowered study) affect the prevalence?

I am doing a meta-analysis where I calculate an overall prevalence value for multiple studies. I have submitted my manuscript to a journal. I used sample size as one of the risk of bias criteria, ...
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2 votes
2 answers
59 views

question concerning Covid infection data reported by the media

I tried searching stackexchange for existing posts about this, but I could not find them. Please redirect me if appropriate. My question is very simple, and perhaps partly related to the observations ...
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2 votes
0 answers
59 views

Prevalence threshold calculations error

I see on this page the formula for calculation of prevalence threshold: Given also are following values on that page: ...
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2 votes
0 answers
87 views

Correction for sample overlap in a meta-analysis of prevalence (metafor package)

I want to conduct a meta-analysis of around 30 studies (from a systematic review). Some background of the studies: The quantity of interest is the prevalence of RSV infection. Different studies ...
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1 vote
0 answers
112 views

Pooled samples: estimating prevalence of disease

Struggling to understand the concept of pooled sampling and estimation of prevalence. Would really appreciate some help to understand this. Example: 0.5% of the population has a specific disease. ...
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2 votes
1 answer
93 views

Optimization of pool size and number of tests for prevalence estimation via group testing

I'm trying to devise a protocol for pooling lab tests from a cohort in order to get prevalence estimates using as few reagents as possible. Assuming perfect sensitivity and specificity (if you want ...
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0 votes
0 answers
9 views

Detect apparent prevalence [duplicate]

I have farms in my dataset and from each farm, I have a few animals (varies for each farm) to test for a disease. I want to know, if I tested these animals, what apparent prevalence will I be able to ...
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Is it possible to estimate prevalence from a given sample size?

I have farms in my dataset and from each farm, I have a few animals (varies for each farm) to test for a disease. I want to know, if I tested these animals, what apparent prevalence will I be able to ...
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1 vote
1 answer
251 views

What is the difference between 1-year partial prevalence and annual incidence?

In cancer research, like in this article, partial prevalence is sometimes used to assess the epidemiological state of a disease in a population. The document I'm trying to understand (link, in french) ...
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