This tag is very ambiguous. Use it when the question is about sample size & the following are NOT more appropriate: [small-sample], [large-data], [power-analysis], [power], or [underdetermined].

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2answers
25 views

Sample size calculation for proportion

I am in a doubt about using Absolute and Relative precision for sample size calculations. Suppose if I want to conduct a study to asses the prevalence of Hypertension in a general population, which ...
1
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1answer
23 views

Can I add more cases and/or predictors to existing set of data?

If I have a set of data with 40 cases and 3 predictors can I add more cases and/or predictors later to the existing set of cases if I want to explore the effect of more possible predictors? The data ...
0
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0answers
34 views

Sample size for logistic regression. How to determine the number need for positive and negative cases?

I would like to apply logistic regression for my research. And before that, I want to calculate the minimum number of sample size, positive cases, and negative cases. ...
0
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0answers
18 views

Sample Size Stumped

I am trying to come up with the best sample size for a QA problem. We are trying to make sure our product stays below a certain threshold. We make 600K products each day and each sampled product is ...
0
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1answer
30 views

cross validation vs. sample size

I am interested in performing GLM regression on a data with sample size of 37. After splitting the data into training (30 obs.) and testing (7 obs.) sets, I'm wondering wether it's better to build one ...
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0answers
18 views

Size of parliament in Lottocracy? [on hold]

Assume you are living in a country with a population of 100 million people. In this country the members of the parliament are not selected by vote but by lot (see Lottocracy). How many members would ...
0
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1answer
16 views

Sample size calculation for the comparison of the means of three groups

I have to calculate the sample size for my project. The study is a comparison between three different treatments at three different time points. The outcome variable takes continuous values. We ...
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0answers
9 views

Sample Size calculation - Find minimum sample size to determine positive effect

I'm calculating the sample size required for an experiment with continous outcome variable. I'm considering two ways to calculate the sample size. One is based on a differences in 2 means test. The ...
0
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0answers
21 views

Sample size calculation - Pros and cons of using one-sided z-test over two-sample differences in means approach?

I'm calculating the sample size required for an experiment with continous outcome variable. I'm considering two ways to calculate the sample size. One is based on a differences in 2 means test. The ...
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0answers
24 views

Minimizing 95% Confidence interval extent for bootstrapped confidence intervals

I'm new to CrossValidated so please excuse any shortcomings in my question. Suppose I have a sample of 500, for a population of 500,000. I asked my sample of 500 what day of the week they go grocery ...
0
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1answer
18 views

IBM SPSS QUESTION: Measure the perception of the respondents

My problem to solve with IBM SPSS is: I have got answers to a question about X topic that contains 15 options of multiple response and I want to characterize the perception of the correspondents ...
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0answers
8 views

Sample size calculation to compare variables from multiple groups [closed]

I'm going to conduct an in vitro model experiment to compare a continuous variable between 5 groups. I would like first to calculate the sample size needed for every group. I have used online ...
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0answers
13 views

Design effect in Cluster Sampling [closed]

I am facing a problem in calculating sample size of survey. When I am adding design effect this in calculation than sample size become increased. Why design effect in important for calculating sample ...
0
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0answers
15 views

Selection model with cross-sectional data(limited sample), make any sense?

To my understand, when someone using the selection model, he make sense just when he properly mimic agent's choice behavior using agent's current characteristics, even in a reduced form. It's not a ...
0
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0answers
23 views

Using G*Power to determine the sample size for an repeated measures ANOVA

I am currently designing an experiment that I want to analyze using an RM ANOVA. Since some of the factors are confounded I need to do multiple ANOVAS. One analysis will be for 2x2 factors (within ...
1
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2answers
71 views

Statistical significance versus sample size [duplicate]

Statistical significance of a (variable in a) model grows with sample size. Citing Gilbert (1986): If one uses test statistics with constant size (i.e. a constant degree of confidence), almost any ...
1
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1answer
14 views

How do you develop Confidence Intervals based on non average data

I am collecting votes from an election poll. The rules for voting allows the voter to select ten out of 36 candidates for election. Any candidate whom receives at least 75% of the vote or more wins ...
1
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0answers
13 views

Does minimum variance imply a maximum for ess?

Does minimum of variance of weights $$ \text{var}(x) = \frac{1}{n} \sum_{i }^n {x_i}^2 - \frac{1}{n^2} \left({\sum_{i }^n {x_i}}\right)^2 $$ imply the maximum of Kish's approximate formula for ...
0
votes
1answer
18 views

Calculate sample size to determine freedom of disease with two level clustering

I'm trying to find a calculation that will allow me to calculate both: the number of farms and the number of sheep per farm I would need to sample to determine the absence of a disease for the ...
0
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0answers
16 views

How many samples is needed

I have a function (F) with n parameters (x1,x2,...xn) all the parameters are defined by normal distributions. I would like to know how many times I should sample F to get a reliable distribution. ...
0
votes
1answer
21 views

Sample size calculation for clinical trial

I am facing a problem regarding sample size calculation of clinical trial. Currently a drug is used at 2.5 mg for adult and ...
3
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0answers
16 views

Measuring “almost the same” when significantly different

The following table is of UK domiciled university applicants to UK universities in $2013$ and of acceptances, grouped by self-declared disability. A $\chi^2$ test on the numbers shows an extremely ...
3
votes
2answers
132 views

Mann-Whitney U test with unequal group sizes and one group very small

I have a sample of 24 participants who gave their responses to 8 questions. I calculated their mean response. Can I use Mann Whitney to compare between 2 groups where one of them has only 2 ...
0
votes
1answer
8 views

Difference in confidence intervals of two sample sizes given a finite population

I can't seem to wrap my head around this problem. My company is commissioning a facility that recovers two types of metal from ash generated from an incinerator: ferrous (metal containing iron) and ...
2
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0answers
30 views

Sample size needed to estimate probability of “success” in Bernoulli trial

Suppose a game offers an event which upon completion, either gives a reward, or gives nothing. The exact mechanism for determining whether the reward is given is unknown, but I assume a random number ...
1
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0answers
19 views

statistical signficance and sample size

I have a question regarding statistical significance and sample size for a website a/b test. using a sample calculator and knowing my control's conversion rate, 80% statistical power and a minimum ...
1
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0answers
30 views

Number of experiments when expected value = probability [closed]

How many times I should conduct experiment to have expected value which will be within some interval (for example 2 SE) of probability. For example how many times I should toss coin so that frequency ...
7
votes
3answers
387 views

Why is type I error not affected by different sample size - hypothesis testing? [duplicate]

I don't understand why the probability of getting a type I error when performing a hypothesis test, isn't affected. Increasing $n$ $\Rightarrow$ decreases standard deviation $\Rightarrow$ make the ...
2
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0answers
22 views

T-test for a small sample with unknown distribution [duplicate]

Consider a simple hypothesis test concerning the mean of a single sample. If the sample is normally distributed and the variance is known, the exact distribution of the sample mean is known ...
1
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0answers
54 views

Required number for logistic regression

I read that it is recommended that for LR, a useful rule of thumb comes from simulation experiments which suggest that the number of the less common of the two possible outcomes (“events”) ...
0
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0answers
5 views

Alternatives in designing regressions with a factor with many levels

Ok, maybe it wasn't the best title! I have a regression analysis in which I want to asses the effect of a discrete var against a continuous one. The problem is that the factor variable has 21 levels ...
2
votes
2answers
41 views

Minimum sample size for 1 way ANOVA?

I have tested a group of participants over various time points and I want to investigate whether mean score on each subsequent time point is significantly different to the mean score at baseline (eg. ...
0
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0answers
10 views

Sample size in the Latin Hypercube simulation to calculate P90, average and P10 and number of variables relation

I am preparing some simulations to determine the P90, average and P10 of a parameter. How many runs do I need to have to get a reliable answer (let's say 5% margin of error and 95% confidence)? It ...
0
votes
1answer
44 views

Determining sample size for AB test with proportion greater than one

So I'm pretty sure I'm thinking about this all wrong, but.. I'm trying to run an AB test on a web platform that will increase the total number shares to a social network (incredibly exciting, I know). ...
0
votes
1answer
42 views

How do I calculate required Sample Size to get useful confidence interval length for Bernoulli random variables?

I am pulling meta data fields from a population of 100M documents. These meta fields include things like Author Name, Author Location, Keywords, etc. Some documents have all of these meta fields, some ...
2
votes
1answer
24 views

How to compare groups with different sizes?

I need to calculate the winner of a PTA membership contest for our local elementary school. There are 15 classes of different sizes (size based on number of students in the class). We need to see ...
1
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0answers
16 views

Retrospective power analyis of lmer for sample size

I'm an MSc student doing an assignment where I am asked to analyze and write up a report on a dataset on environmental enrichment in zebra finches. Among other things we are being asked to do a ...
1
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0answers
16 views

What factors influence the point at which a sampling distribution is said to be nearly normally distributed?

What factors influence the point at which a sampling distribution is said to be nearly normally distributed? *Note that the answer I am looking for is not sample size. I am asking what decides how ...
0
votes
1answer
47 views

How to go ahead with sample size selection when population is small

I have sent a survey to 92 persons but so far I have received only 40 responses. By using sample size requirement calculation I need 75 responses for the desired criteria ...
1
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1answer
97 views

Increasing sample size with bootstrap sampling

I'm trying to perform some classification analyses with a relatively small dataset (201 observations, 32 predictors). There are 8 classes in my data with unequal sample sizes ranging from 10 in the ...
0
votes
1answer
53 views

Calculating sample size of a mixed ANOVA in R (2 between, 1 within variable)?

I'm searching for a built-in function in R for calculating the required sample size (given certain power, alpha,..) of a mixed ANOVA (2 between, 1 within variable, 2x2x2 design). Does this function ...
2
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0answers
43 views

Does Hoeffding's inequality apply to sampling from finite populations?

Based on Hoeffding's theorem, one could easily find the minimum number of samples required for the inequality $\Pr \left(|\bar{X} - \mathrm{E} [\bar{X}]| \geq t \right) \leq \delta$ to hold as ...
2
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0answers
26 views

Sampling Size for a large Dataset

I am having a dataset of size upwards of 200 million rows. I have no knowledge of the distribution of this dataset. Would like to perform some analysis on this - like look at the ...
0
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0answers
16 views

Compute effect size based on simulation using different lists of different length

For my research purpose I wrote a small simulation to compute an empirial p-value based on an input gene list and a reference gene list. The idea is to check for each gene in the input gene list, the ...
0
votes
2answers
29 views

Choosing samples of different sizes - considerations?

Let's say I have four populations with the sizes 2451, 2117, 7577, and 1545. Each of these are sets of activity sequences on which I do sequence analysis. Based on this I want to do clustering based ...
0
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0answers
17 views

Sample size calculation using G*power for a mixed design

I have performed a pilot study in form of a 2x5 mixed design, with 10 participants. The factor with 2 levels was applied as a between subject factor, meaning that only a half of participants were ...
-1
votes
1answer
30 views

Sample Size Calculation of Pilot Study

I want to calculate the sample size for my pilot study. My subjects will undergo a certain test once taking a substance before the test, once taking a placebo. My goal is to find out if the substance ...
1
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0answers
12 views

Balance checking in randomized controlled trials with large sample

I have a survey experiment in which the treated group receives a certain prompt that the control group does not. I also have a bunch of demographic variables that I want to check for balance between ...
1
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0answers
18 views

Upper bound for sampling fraction for CLT to hold

What is the upper bound for the sampling fraction for the Central limit theorem to hold when sampling without replacement? Context The context for my question is that it is regularly argued (see e.g. ...
1
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1answer
60 views

How to calculate sample size for this study design?

I am trying to find out whether the number of participants I recruited (N=42) so far is sufficient for my study in which: there are two interfaces (say A and B). ALL students in the study will try the ...