Questions tagged [prevalence]
The prevalence tag has no summary.
50 questions
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My boss does not approve of Bayesian revision for PPV, NPV etc. and insist on the simpler formulae. How to change their mind?
The model compares costs and outcomes of two diagnostic tests that are used on the same population for diagnosis of a condition. Sensitivity and specificity of each test and the prevalence of the ...
0
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0
answers
44
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Meta-regression of long-term changes of prevalence data over time
I am investigating whether we can detect any long-term directional changes in the prevalence of a set of diseases. I am also interested in finding disease characteristics (for example transmission ...
13
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3
answers
316
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What is the first known example of a proportion being calculated to characterize a human population?
The title more or less nails it. Am really interested when the first recorded use of a population proportion (aka prevalence) based on some kind of data collection. I imagine this may be very old (e.g....
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1
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2
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Is it possible that false-positive rate decreases with increasing prevalence?
I am interested in the effect of prevalence on prediction performance. Chouldechova (2016) states that:
[w]hen using a test-fair [recidivism prediction instrument] in
populations where recidivism ...
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0
votes
2
answers
78
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On choice of y-axis range for visualization
Let's say that a disease has low prevalence. The prevalence is the proportion which should range from 0% to 100%. I want to visualize the trend of prevalence over the time. (Let's assume that ...
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2
votes
2
answers
185
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Prevalence upper bound when no events are observed in sample
In a sample of 2000 observations, no positive cases were found, but I want to still be able to provide an upper bound for the prevalence.
The general rule that people seem to use is to simply take 3/n,...
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0
votes
2
answers
134
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Relationship between sensitiviy, probability of detection and Prevalence
Folks, I have 3 questions:
If I know the number of exams performed with a specific test on a group of patients and the test's sensitivity, can I directly estimate the overall probability of detecting ...
4
votes
2
answers
280
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What data are used to find the final threshold for a medical diagnostic test?
Suppose I have some blood measurement X whose values correlate with some disease Y (so people with the disease use to have larger values of X). Moreover suppose that the disease is rare, say 1% of a ...
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1
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0
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87
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Sample size calculation for prevalence studies: how do I find d when reviewing a published study?
I have found the following formula in Munn et al.:
$$N = \frac{Z^2 P(1-P)}{d^2}$$
$N$ = sample size
$Z$ = statistic for a level of confidence
$P$ = expected prevalence
$d$ = precision
The problem I ...
4
votes
2
answers
97
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Accounting for recall period in proportion meta-analysis
We are conducting a meta-analysis of "prevalence" of event-type exposures, e.g. "have you been physically assaulted in the past X months". We are trying to adjust for different ...
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1
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0
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R survey package: compare weighted prevalence with literature result
I have a large dataset (>3000 cases) with results of serological tests. Based on these results i want to calculate the weighted prevalence of the disease. The data is categorical (0 = disease ...
1
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0
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85
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Prevalence / Incidence and Relative Risk
I'm doing a course in biostatistics and I came across this question to solve:
"Consider a two-year follow-up study of the association between a measure
of stress (dichotomised into two levels: ...
0
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0
answers
68
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Appropriate statistical test evaluating difference in proportions between two groups over multiple time points
Over the course of a year, I took samples from dogs and their beds and looked for the type of bacteria in the bed and in the dog every month. I did not get samples from the same dogs or the same beds ...
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1
vote
1
answer
55
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Adjust a crude rate based on observed prevalence within population [closed]
I have data such as the below:
Area
Admissions
Population
Crude rate per 100,000
Cambridge
137,204
1,077,382
12,735
London
111,896
1,013,985
11,035
I have been asked to 'adjust the crude rate for ...
1
vote
0
answers
48
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Age Adjusted Prevalence at region level with only country-level population distribution
I'm trying to calculate age-adjusted prevalence for a bunch of different chronic diseases from hospital data in a specific area and I'm having some difficulty. I have total country level population, ...
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1
vote
0
answers
121
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Accounting for overrepresentation of positives in binary classification test set for calculation of precision and recall
I have a binary classification task with highly imbalanced data, since the class to be detected (in the following referred to as the positives) is very rare.
For data limitation reasons my test set ...
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2
votes
1
answer
532
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Calculating the confidence interval or standard error of a PPV adjusted for prevalence
I am trying to evaluate how well a disease test performs in a case-control study. In this example, the prevalence is 0.5%, and the results are below:
Disease +
Disease -
Test +
40 (TP)
10 (FP)
Test -
...
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1
vote
1
answer
86
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What is the probability of at least one person in a sample of k people being infected?
Given the prevalence, sensitivity and specificity of a single test are known.
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1
vote
0
answers
52
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Infection rate time-series analysis
We have some surveillance data from a hospital that include infections with antibiotic-resistant bacteria and the number of admissions, patient-days so that I can calculate incidence and prevalence. ...
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1
vote
1
answer
664
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How to estimate disease prevalence using logistic regression when some people are measured several times
I have a binary variable indicating the presence or absence of a disease as well as variables for time and other covariates. SOME (not all) people are observed (tested) several times.
Suppose I want ...
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2
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0
answers
114
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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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8
votes
2
answers
2k
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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
287
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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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0
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0
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51
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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
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1
answer
168
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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 ...
- 1,173
1
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0
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126
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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:
...
3
votes
1
answer
237
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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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3
votes
1
answer
122
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0
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1
answer
116
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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 ...
1
vote
1
answer
114
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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 ...
4
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2
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612
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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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0
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0
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124
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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
vote
1
answer
123
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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
0
answers
40
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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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9
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3
answers
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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
547
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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?
0
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2
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74
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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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0
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0
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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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3
votes
3
answers
309
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Why do some researchers use the oxymoron "prevalence rate"?
An incidence rate (whether an incidence density or an incidence proportion) measures the probability of an event (typically a new case of the relevant health condition in epidemiology) divided by time....
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1
vote
1
answer
145
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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
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2
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123
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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
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0
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346
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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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3
votes
0
answers
275
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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
378
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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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3
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1
answer
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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
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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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0
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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
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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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0
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How to convert annual rate and SD to monthly rate and SD? [closed]
If I assume that a survival rate and its SD remain roughly the same for each month, how do I convert an annual rate and SD to a monthly rate and SD? All I know is the annual rate and SD, and the ...
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1
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0
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Defining the size of control group in chi square statistics
I'm trying to compare the prevalence rate of autism in offspring of mothers with and without gestational diabetes. I gathered data from 1000 women, 8 children have autism (prevalence rate 8/1000). ...
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