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Questions tagged [proportion]

A proportion is the fraction of some total that is of a particular kind, either (i) as a count of one type of thing out of a total count, or (ii) as a component of a continuous variable.

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How to calculate the variability of proportions?

I need to find the proper sample size, and I have found formula in the Stanford lectures. But I can’t understand what the “variability” of proportions means in this case. Consider two proportions : ...
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Calculate proportions and CI [on hold]

My data is in two columns: sample, and disease, and 380 rows. How can I calculate the proportion of disease and the 95% CI for each row in R
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Power of Tests for Proportions: One Proportion vs. Two Proportions

I am trying to calculate the required sample size for a trial, where my outcome is proportions (for each subject I am measuring if the subject had an event or not). I tried two ways and got different ...
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How to find the p-value for this hypothesis test for two proportions?

I can't find the answer for this problem. In the answersheet it suggests that the Z-score is -20.5, but I can't understand how it's been calculated. : A 2012 survey of 2,254 American adults ...
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When to use Chi-squared and when Z test for categorical variables?

The problem is: There was a survey conducted among 1137 adults from California, Nevada, and Oregon. They were chosen randomly and they answered to the following question “Do you think Marijuana ...
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Sample size for proportions and fisher exact test

I need some clarification. I am doing a chart review. Plan to test significance with fisher exact as its two interventions, one yes/no outcome. Presumed prevalence in the population is 15%, but ...
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Meta-analyzing rates of change in one variable observed in one group over time

I'm working on a meta analysis of prospective studies assessing changes to mental health in the year following an event. For the purposes of example, say it's the prevalence of major depressive ...
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Sample Size Experiment Proportion Failure

I have N machines and I want to implement an experiment E in them in order to improve their proportion of failures. However, I’m not sure yet if this experiment E will increase, decrease or do ...
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Sample Size Proportion Comparison Test Finite Population

How can I calculate sample sizes for a Prorportion Comparison Teste of Finite Populations? Is there a function in R? Basically, I want to know what is the finite population version formula for the ...
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How to compare two small sample proportions using R?

All the data is in the attachment below& The question is: Do these data provide convincing evidence that there is a difference in how good people are at recognising the backs and the palms of ...
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GLM: Modelling proportional data - account for variation in total sample size

When I am sampling the proportion of a sub-group of animals to the total number of animals within a sample, I can feel quite confident (after taking into account environmental factors) that I have a ...
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Statistics for a probability parameter

I am measuring how humans perform a perceptual test. The graph shows the proportion of correct responses as a function of an independent variable x for one person. The model includes a lapse ...
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1answer
132 views

Analysis of count data with percentages

for my master thesis I count and identify sediment grains. In total I have 82 samples from 3 different gravity cores. I divided the sediment components in 11 groups (Quarz, Mica, Opaque, Aggregate, ...
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Comparison of 2 treatment groups using proportions

I have two treatment groups (lets say A and B) with pre/post data for two diffirent populations and there are statistically significant differences (p<0.05) between before and after treatments, ...
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Visualising a table of proportions

I have a table like ...
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1answer
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How to infer difference of population proportion between two groups when proportion is small?

I have a dataset where the issue is of this form. There are two groups, Group A (N=5000) and Group B (N=1000). Let's say 5 people in Group A develop a certain disease, and only 2 in group B do. Then ...
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How to allocate unclassified observations proportionally within classified data?

In my dataset, about 30 percent of all observations belong to a unclassified category. Since I want to account for the effect of these observations, I want to allocate these unclassified observations ...
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How to identify the difference in significance of two different z test for two proportion test?

I have two cell types (A and B) in a tissue. I have 5 replicates of RNA sequencing data in control and treatment condition for cell type and B separately. We are interested in identifying genes which ...
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Comparing frequency counts

I have data that contains frequency counts for how many times somone opened an item. I'm comparing data for nov and dec. ...
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37 views

one sample z-test standard error

Let's say I make the claim that 9 out of 10 dentists recommend a tooth paste. Next, I can ask 1000 dentists, and let's say that I find 700 / 1000 acually recommend it. so here $p_o = 0.9$, and $p = ...
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Sample is almost the same as the population

I'm interested in a situation where I have a small list of events, somewhere in the range ten to a few hundred. Each event can be a 1 or 0 outcome. I have a good reason to believe that the factors ...
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How to simulate sample proportions near or at zero in a Monte Carlo simulation?

I am running a chain of Monte Carlo simulations to estimate uncertainty in some model estimates (which are derived from a series of estimates). An important variables used in one of the steps is a ...
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Best way to compare changes in proportions

I am reviewing a manuscript so I cannot be specific but the authors had a treatment that was supposed to improve access to care. They had a treated group and a control group. Access to care was ...
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Unequal sample size for 2 proportion calculation group

I have a question. It’s about the uneven sample size between 2 groups. Let say I want to compare & analysis these 2 groups when 1 of them have small number of sample. To give you some light, here ...
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108 views

Relationship between Beta regression of Y on X and linear regression of X on Y. (where Y is a proportion)

I am trying to model the relationship between school district funding and a district's poverty rate. If I treat funding as the independent variable then the dependent is a proportion on [0,1]. This ...
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1answer
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Comparing the distributions of proportions in two groups

I'm comparing the total dog population in a region with the number of dogs in rehoming centres in that region. The data are below. The number of cases is the number of dogs that have been in rehoming ...
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Appropriate regression to predict >2 fractions?

Let's say I have demographic data on various classes and the proportion of students in the class who are black, white, etc. I'm trying to create a regression to determine features of the class that ...
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1answer
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R: generalised additive model on proportional data

Introduction I am analysing temporal population data on the amphipod Orchestia gammarellus. At several moments each year, all animals were collected from a small spot, and several life history traits ...
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1answer
21 views

Sample size for the normal approximation of the Binomial distribution

I am reading about the familiar hypothesis test for proportions, using the normal approximation for large sample sizes. Some people say (write) that the condition for using the approximation is np>5 ...
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1answer
28 views

Sample size needed to prove equal proportions

We are trying to prove that three groups have the same proportion of some effect. We are struggling with formulating the null hypothesis, and whether or not the sample size is big enough. The ...
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1answer
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Proportion Test: Z-test vs bootstrap / simulation - different results

I'm learning hypothesis testing, and going through the following example: The CEO of a large electric utility claims that 80 percent of his 1,000,000 customers are very satisfied with the service ...
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Overdispersed proportion test?

I am comparing proportions in genomic data. In particular, I compare two populations, A and B, and I look at genetic sites. In other words, I have N contingency tables ...
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Test for yield and disease incidence in block design

I need to analyse a set of data coming from an agricultural experiment, with the intention of assessing the incidence of a certain disease in potatoes under three different treatments (plus blank). I'...
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1answer
56 views

How to calculate the error of percentages

Is it correct to calculate the standard deviation of percentages/proportions as you would for four numbers (i.e. non-percentages)? Thanks for your help @user2974951 @whuber and @asdf. Yes, you're ...
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Find significance between two group proportions

My question is the following: what statistical test would I use to compare the proportion of participants between two groups. For example, if in 2009, 20% of participants ( population was 55) to a ...
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group sequential design for one proportion

I would like to create a group sequential design for a one proportion to test H0: p=0.97 vs H1: p=0.98 with alpha=0.3 and beta=0.43. Above specification provides me the sample size of 120 for a ...
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GLM for proportion data in r - with many zeros (or ones) [duplicate]

My understanding is that generalized linear modeling (GLM) is recommended for proportion data. However, this seems to run into problems when a set of data is full of zeros (or ones). For example, a ...
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which stat test?

I am doing a health interventional study in the community. I calculate the "pre-intervention" proportion of behavior of the community before applying the interventions. And after 1 years of various ...
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1answer
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Get better confidence interval by drawing multiple samples

Imagine that I have population of size N and I draw a sample of size n from which I compute a proportion $\hat{p}$ of a categorical variable. And I want to get a confidence interval of 95%. So I ...
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Calculating a Confidence Interval for a Proportion for a Sample of Different Size

I'm interested in a (preferably analytic) solution or approximation to the following problem: Let $s_1$ be a sample from an unknown distribution of size $N_1$ and with proportion of successes $p_1$. ...
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Comparison of proportions using McNemar's Chi-Square using Pre- and Post- data for two disease conditions

This question follows-up on the post: What is the difference between McNemar's test and the chi-squared test, and how do you know when to use each? I am examining a pre- and post- intervention data ...
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Comparing proportions from overlapping samples

I'm looking to compare the read rate of an email newsletter with the read rate of another newsletter. However, many (not all) of the people who receive one newsletter also receive the other. What ...
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Test a proportion against unanimity

How can I test a proportion against an expected value of 1.0? Made up example (slightly silly): Dichotomous Yes/No question... Would you like me to hit you very hard on the head with this hammer? ...
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Distribution for average of multiple binomial proportions

Assume we have a population $N$ and a proportion $p$ of that population with a characteristic of interest. Both $N$ and $p$ are unknown. Furthermore, assume that we have $k$ random samples $(n_i, x_i)$...
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Modelling percentage and proportion data with GLM's [duplicate]

I would like a simple answer, if there is one, to a question I cannot seem to find on here. What is the best way to model percentages? Say I have a glass that is empty and I fill it with liquid ...
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Comparing Test and Control Lift in Proportion

I have two groups - a test/treated and control group - for which I am trying to assess whether the lift or percent change in proportion from a pre to post period between the two groups are unequal. I'...
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Comparing survival rates

The question I have is focused on comparing remission rates at a fixed point in time. For example, I have cancer type A and cancer type B (the two are not mutually exclusive groups) and all patients ...
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1answer
52 views

Where is my potential flaw in my Z-test of Proportions?

I was working through this z-test of proportions example I found online. The online example solutions says that the difference between the groups is statistically significant, whereas I concluded it ...
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41 views

Is lmer or glmer appropriate for nested continuous proportion data

I have a reviewer that wants me to analyze my data along the lines: Con_Ratio ~ Range * Latitude * Longitude + (1 | Genotype/Pair). But I'm not sure if this can be done and how. My experimental ...
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specific equation for modified wilson confidence interval

I recently read the Brown, Cai, Dasgupta paper on interval estimation for a binomial proportion where they propose the modified wilson method as a better alternative to the standard wald interval. I ...