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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Association between two proportions using p-value

I have this two proportions that I need to see if they are associated somehow. Null hypothesis is that they are equal. I'm using R. So I get the pooled proportion ...
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9 views

1 sample z test of proportions

We are trying to work out whether what we currently do is accurate. We want to work out if a proportion (% scoring 5 on a 5 point scale) are significantly below a target score. Normally a 1-sample ...
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16 views

proportion and stats [on hold]

A study of accident locations on a level, 6-mile bike path shows that accidents occur uniformly along the length of the path. There is a stream alongside the bike path between the 3.2 mile-mark and ...
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1answer
39 views

Statistics on tastings

Some people at my workplace have had some fun lunch discussion as of late, concerning some people's alleged ability to taste the difference between things one thought one shouldn't be able to taste a ...
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1answer
38 views

Using proportional data with a binomial error structure in R… a worked example needing answers!

I am trying to test if the proportion of herbivores in spider's diets is related to the proportion of herbivores in their grassland, but am struggling to understand if I should be using a binomial ...
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1answer
69 views

Solving formula for confidence intervals on two proportions

I'm interested in comparing two independent proportions from two samples. The formula for doing so is available in the Internet (e.g. here). So far, so good. But my main purpose is not to build a ...
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6 views

Website Conversion: how to calculate confidence interval for tomorrow's conversion rate

Let's say I have a website with certain number of visits per day and conversion events: ...
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1answer
34 views

Testing small proportions

My data is made up of 4 groups, each with a large and identical sample size of 20,000. The number of successes in each group is fairly small: ...
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9 views

Estimating variation in a given proportion across multiple experiments

I have stimuli which vary (lets say that the stimuli range -10 to + 10). I also have a single reference stimulus (value = 0). I want to measure the accuracy with which people can discriminate each of ...
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32 views

Power of a test

I need help with the exercise below: To investigate the effect of a new vaccine, 150 out of 300 sick animals were given the vaccine and the remaining 150 were given nothing. After a while, 10 of ...
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3answers
113 views

Which statistical test to use when comparing two ratios?

I have five independent experiments. In each experiment I record the intensity of sample A and sample B, then add these intensities together and calculate A and B as a proportion of the total. ...
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7 views

Test on proportions on low volume data

I have a data where I try to test the hypothesis about proportions for 2 group of patients. In 1st group I have 21 patients with 6 of them having necessary condition while in 2nd I have 7 patients ...
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1answer
37 views

H to check if proportions in two small samples are the same

I have two small samples denoting if something occured or not. For example: $s_1=\left(1,1,1,0,0,1\right)$ $s_2=\left(1,0,0,0,0,1,1,0\right)$ I want to test if proportions of occuring $1$ are the ...
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111 views

Why is independence required for two- sample proportions z test?

I read in several books as well as in different posts (e.g. here) that independence is required for two-sample proportions z tests. But so far I could not find an explanation why this is the case and ...
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37 views

Two-proportion z test: is it best for my problem, and can I pool data from multiple “replicate” populations?

I am examining populations (cultures) of yeast cells and scoring them for a particular trait. The data is categorical; within a population, a yeast cell either has the trait or it does not. I wish ...
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26 views

Time series model of prevalence

I have a collection of samples from which I have estimated prevalence on an annual basis using a logistic regression model. The response variable is whether or not the focal species was present in ...
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26 views

Difference in proportion: Pre-post intervention-control study design

I am conducting a meta-analysis where I want to compare the proportion of samples pre- vs post- intervention. To do this, I have been calculating the difference in proportion (Post - Pre) as the ...
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18 views

Test statistic and C.I. for population proportion

I'm doing a test statistic and C.I. for population proportion. Can someone explain to me what are assumptions coming from hypergeometrical distribution directly to normal distribution? As I ...
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1answer
35 views

Hypothesis testing for 2 proportions - for A/B testing

I was trying to understand the statistical tests to use during A/B testing and stumbled upon this documentation of the Amazon A/B testing SDK: ...
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2answers
58 views

Which test to use to check the difference between samples of percentages?

I have data measured from 14 samples between two conditions. I want to check difference between them. But the data is normalised and is in terms percentage (0-100). For example ...
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13 views

Proportion test in more than 2 groups

Is there any test with appropiate statistic that enables to compare more than 2 groups in terms of proportions of successes in each group? I have 30 groups with calculated fractions of successes in ...
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1answer
32 views

What type of test should be used?

What kind of test would I use to find the answer to this? Is there evidence that cereals promoted in an in-store circular have a higher average number of units sold per store than cereals not ...
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23 views

Need clarification on a passage. (Autism Prevalence)

Passage verbatim: According to a review by Silverman et al. (2010), the incidence of autistic disorder is 0.6–1.0 percent in the population. The disorder is four times more common in males ...
3
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1answer
87 views

Confidence interval for a proportion

Let's say I want to built a confidence interval for a proportion ($p$). I have seen that many times this is made from the standard error: $p\pm 1.96\times SE(p)$ taking SE from ...
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19 views

power of chi squared test for two proportions with gsDesign package in r

I have problem with calculating power for two sided chi squared test for the following design: Study includes 200 patients (100 patients per group). The null hypothesis is that p1=p2=30% and ...
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2answers
78 views

Compare differences in dependent frequencies

I would like to compare two error rates (proportion of incorrect answers in questions with dichotomous response-format) for two different items, and I am looking for some advice on how to do that. ...
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0answers
46 views

McNemar or chi-square - test for group differences paired and unpaired data

I understand that the difference between a chi-square test of homogeneity and the McNemar test is that the chi square is used for unpaired data and the McNemar is used for paire data. Here's my ...
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1answer
51 views

Proportions Test for when one sample has lots of zeros

I tried using chi-squared test, but it is giving me odd results, For example: Let's say that I am testing whether behavior between male and female users is the same. Males only bought 3 units of ...
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1answer
32 views

Performing significant difference tests in endline evaluation

we have conducted an endline survey and now comparing the result with baseline survey. I am interested to find significant difference between baseline and endline. One of sample questions is given ...
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1answer
51 views

Analysis where dependent variables are proportions

I have a set of demographic data (age, race, social class, etc.) for selected geographic areas. These independent variables are each proportional in each type, i.e. Area A: White 70%, Black 20%, Asian ...
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43 views

Difference between two proportions

How do you compute the difference between two proportions so those differences can be further analyzed? I have some repeated measures data with a first and second data point per subject, and I want to ...
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1answer
266 views

Exact two sample proportions binomial test in R (and some strange p-values)

I am trying to solve the following question: Player A won 17 out of 25 games while player B won 8 out of 20 - is there a significant difference between both ratios? The thing to do in R that ...
3
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2answers
120 views

Proportion data - beta distribution v. GLM with binomial distribution and logit link

I have a fisheries dataset for which I have calculated value for each grid cell on a map. The value is the proportion of the total fishing sets in that cell for each month/year. So, I have values ...
2
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1answer
86 views

How to compare the proportion female with the proportion male

I would like to know if it is correct to do the following statistical comparison: In a sample of $440$ patients, I have $241$ females ($54.8\%$) and $199$ males ($45.2\%$). Are these proportions ...
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1answer
17 views

problem: a sample size for the assumed effect in the 2 sample proportion test

I would like to calculate a sample size for the 2 sample proportion test when the significance level is assumed (0.05), power is assumed (0.90) and I'd like 2 sample proportion test to detect that ...
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27 views

How to analyse binary outcome data with between- and within subjects factors?

I am looking for the right statistical procedure to analyse my data (mixed design) with binary outcomes. Between-subjects variable: treatment (yes or no); experimentally manipulated Within-subjects ...
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14 views

Proportion (difference) test for drifting proportions

Two machines are spitting out coins (at different non-constant rate). The probability of flipping heads for every machine is believed to change very slowly in time (compared to flipping rate). It is ...
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30 views

Test of proportion vs logistic regression

Basically I have count and proportion data and my explanatory variable is treatment groups (not really but functionally same thing), the information can be summarised in a 2x2 contengency table. I am ...
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modeling a proportion with seasonality removed

I have a time series of proportions that typically fall in the 0.01-0.05 range. I had intended to use GLM to model these proportions, but I ran into trouble when I needed to first remove a strong ...
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1answer
23 views

Confidence Interval for the average of a set of proportions

If I have a dataset of 500+ observations (people in this case) that has the % of allotted dollars that were spent for each person (so, I have each persons allotted dollars and their dollars spent), ...
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16 views

Population proportion and confidence interval estimation

Q. A disease can be classified into four types. A random sample of size n=100 patients contains $n_1=70$ patients with type 1 disease, $n_2=10$ patients with type 2 disease, $n_3=15$ patients with ...
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multilevel mediation with a proportion dependent variable sem

I am attempting to test an indirect path in a multilevel dataset with an outcome that is a proportion. The data are a collection of variables related to various qualities of potential support ...
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38 views

Questions about non-standard test statistic for difference of two population proportions

Background I'm considering the number of observed 'successes' $x_1$ and $x_2$ from $n_1$ and $n_2$ independent trials respectively. These counts can be considered realisations of random variables ...
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32 views

Confidence intervals of proportions for clustered data

I am trying to compute the proportion of "yes"'s in data that is clustered (participants within cities). If I ignore the cities, I get very nice and narrow confidence intervals. If I compute the ...
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0answers
17 views

Estimating proportions in a non-nested multilevel Bayesian model

Data: x: 1/0 successes (~ 800 data points) c: city code (1 to 78) t: "time of measurement", 1 (morning), 2 (afternoon), 3 (evening), 4 (night) The problem: I would like to estimate the ...
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1answer
37 views

Three proportions testing null hypothesis

I have the following question. In a random sample of 250 people with low incomes, 155 are in favour of a new piece of legislation, while in random samples of 200 people with average incomes and 150 ...
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10 views

Scaling Specificity to larger data set

Suppose I have the following 2x2 table ...
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15 views

probability of sample proportion

I am trying to find the z-score for a sample proportion of 0.39 (The question is actually asking to find the probability of the sample proportion that is greater than .39). The only information ...
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1answer
23 views

Measurements from two raters. Should I use multilevel/“random-effects” model?

I have several variables that were measured on patients, for most patients the variables of interest were measured by 2 independent "raters". Most of the variables are binary. I need to compute the ...
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16 views

Rate of change of sub-population relative to that of the whole population.

I have data for the population size of a community, every five years for the last sixty years. The size of the population fluctuates, but generally increases over time. I suspect however that the ...