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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11 views

representative samples formula [on hold]

I have just started working in quality management and I need to work out a representative sample of a given population of inputs needed for our production to assess them i.e if the bottles we get ...
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3answers
143 views

Sample size calculation for correlation study

I am planning a study to assess the correlation of perceived stress in medical students and their academic performance. After a literature review, it appears that one previously done recent study has ...
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0answers
32 views

Skewed data, unequal n - advice?

This is the first time I have dealt with non-normal data (lucky me!), and I have come to a bit of a road block as to what tests to run. Experiment: Investigate whether false feedback affects ...
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1answer
29 views

How can I find out the needed sample size

I'm going to study if medical reconciliation diminishes the amount of inappropriate medications amongst elderly people in a small part of Sweden. I will count the number of inappropriate medications ...
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0answers
27 views

T-test formula when population standard deviation is known [duplicate]

I got this question from my mentor. Marks obtained by 10 MBA students in Statistics paper (out of 50) is given below. 20.5, 18.25, 10.23, 15.47, 35.62, 47.64, 12.30, 29.65, 38.5, 14.79. Test whether ...
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1answer
13 views

Sample size estimation for MANOVA

I am trying to run a replication of a study which used a factorial design (2x2) with three DVs (dependent variables) and subsequently ran three ANOVAs to test their hypotheses. Given that the DVs in ...
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0answers
46 views

How did they power this study? (One sample proportion test)

I was asked to perform a sample size calculation for a study with a single arm and a binary outcome. They have given me an assumed proportion, $p$, and need the upper 95% confidence interval to be ...
2
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1answer
51 views

I want to take a decision on two gaussian distributions, what approach can I take?

I observe a one dimensional random source, which could be any of two Gaussian distributions with a different set of parameters that do not change over time. They have a the same variance and a ...
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1answer
27 views

Two way ANCOVA with slight heteroscedasticity

I am about to perform a 2-way ANCOVA but I reject the null hypothesis in Levene's Test with a p-value of 0.023. See standard deviation and sample sizes below. I googled up and down and found people ...
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11 views

Manufacturing Process Validation - Sample size calculation

I am new to manufacturing process. Can someone help me to determine the sample size required to perform Manufacturing Process Validation? I know nothing about six sigma, so simple answers are highly ...
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0answers
30 views

Sample size selection discrete case

I have an algorithm that predicts either 1 or 0 , not prediction value like 0.25, or 0.58 or 0.92 or anything like that. I am wondering what is the formula for sample size selection during the ...
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0answers
23 views

t-test with unequal sample size, very large group and very small group [duplicate]

If I have data for 2 group with unequal sample size, first group $n_1=81$, second group $n_2=72000$. Can I still do a t-test for comparing the mean difference between these 2 groups?
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1answer
28 views

Problems due to analyzing variables from different levels at one single level

Please ease the following paragraph from the first chapter , Introduction to Multilevel Analysis , p.3 of the book: Historically , multilevel problems have led to analysis approaches that moved ...
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24 views

Computing Required Sample Size to Control Type II Probability

Let $X_1, \dots, X_n$ be a random sample from $\mathcal{N}(\mu_0,\sigma^2)$, $\mu_0$ known, $\sigma$ unknown. Consider $H_0:\sigma^2=\sigma_0$ vs $H_1:\sigma^2=\sigma_1^2$ where $\sigma_1 < ...
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0answers
10 views

Research Model for Two Samples

I am currently doing my undergraduate research, which entitled the relationship of board composition and financial performance in growth firms and mature firms. I need a help to find the best research ...
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2answers
56 views

What will be the t-value if my sample size increases to an infinity compare to z value?

I do not know where to check this. Any reference/help is much appreciated. If the sample size, n increases to an infinity then will the t-value be larger/smaller ...
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0answers
21 views

Have I interpreted the effect of a confounding variable correctly?

I'm interested in whether feeding rate differ between two species of birds, Species A and Species B. However, tide also affects their feeding rate, and so tide is a confounding variable. In the plot ...
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0answers
29 views

Power Analysis for Logistic Regression with one nominal variable

How do I estimate sample size or do power analysis for logistic regression with one nominal independent variable? Is there a way to do it with Stata?
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3answers
43 views

How many samples needed to approximate true mean?

If I have some arbitrary random variable with true mean $\mu$ how many samples from its distribution do I need to take such that the empirical mean $x$ approximates $\mu$ within an error of less than ...
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0answers
28 views

Rule of thumb for sample size for mixed-effects logistic regression analysis?

Is there a simple way of calculating the minimum number of participants (and/or items) needed for a mixed-effects logistic regression analysis? In particular, what should I do if I don't know what to ...
2
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1answer
48 views

Information criterion for selecting sample size when modeling tails

I want to model the left tail of an unknown distribution with a Generalized Pareto distribution. Somehow I have to select how much of the tail to model. I am wondering if it is possible to create an ...
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0answers
16 views

Comparing differences in pairs of ratings using a bootstrapping like approach

I'm pretty new to bootstrapping like approaches. So I do apologize for any inconvenience. I have two independent samples, snow (n=120) and nonsnow (n=608), consisting of pairs of ratings on a ...
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1answer
40 views

Mulitivariable regression?

For my research project on the effect of a specific kind of surgery on clinical outcome, I want to study the correlation between the improvement in clinical outcome scores (ie the difference between ...
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0answers
26 views

Incidence rate sample size

Hi am trying to reproduce the following computation from a paper, but cannot acheive it. Sample size calculation was based on the combined incidence rate of moderate and severe hypoglycemic events ...
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0answers
53 views

Relative size of p value at different sample sizes BUT same odds ratio

Will the relative size of the p-value increase or decrease with the increase of sample size? My guess is that it will decrease, however, would it be the same case if they both have the same odds ratio ...
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1answer
25 views

How are sample size and confidence related when calculating Sample mean?

Maybe I'm getting ahead of myself and I should just keep reading my textbook, but I'm getting confused about something. Let's say a friend gives me 10,000 integers that he claims are normally ...
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28 views

What is the sample size when we take repeated measures?

Say we're running an experiment and we have 10 volunteers. From each of these 10 volunteers we take 3 measurements. So we end up with a dataset that has thirty rows. Say we're writing up the results. ...
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13 views

Beta regression sample size / power calculation

I'm looking for sample size calculation for beta regression with logit link. Could somebody give a link to a paper about it, or explain how it is done?
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0answers
22 views

Normalize(Scale) data before sampling or after sampling in binary classification?

I have a binary classification database with imbalance outputs (1 labeled data: 1400 samples, 0 labeled data: 200 samples). I balance data based on a criteria to (200 - 200). Where should I normalize ...
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0answers
29 views

Sample lower bound for binary classification in Linear Discriminant Analysis?

Below is a description of this problem: Suppose the label $Y\in\{1,0\}$ in binary classification satisfies $\Pr[Y=1]=\Pr[Y=0]=\frac{1}{2}$, and $p(X|Y=1)=\mathcal{N}(\mu_1,\Sigma)$, ...
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39 views

p-value and sample size [closed]

What would be the the p-value for a $\chi^2$ test when $n = 90$ when the p-value is .052 for $n = 60$?
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1answer
29 views

Unequal sample size one way ANOVA

I want to compare the means of X between BMI groups, but have unequal sample sizes between my groups. ...
0
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1answer
38 views

Apparent paradox about using a pilot study to determine sample size

I'm using some pilot data to determine the necessary sample size for an upcoming study. The primary goal of this study is to measure the correlation between two variables, A and B, and to determine ...
3
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1answer
74 views

Sample size when fitting categorical survey data

I have a model which fits data from repeated surveys: at time $t$, a number $n_t$ respondents is asked a question and can give one of $K$ answers ($k=1, ..., K$). This is repeated $T$ times ($t = 1, ...
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0answers
41 views

Sample size needed to validate classification/prediction model

Dose any rule of thumb exist (or possible calculation) regarding sample size needed to validate an binary classification model. We have developed this prediction model for a medical condition and ...
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4answers
41 views

Sample size of sampling distribution of the sample mean

When people say that the mean of the sampling distribution of the sample mean is equal to the population mean, is this true regardless of how small or large the size of the samples are? I'm having a ...
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0answers
18 views

Time-partitions of sample size

I am struggling with explain something I read in a Whitepaper. The essence is as follows. Let's begin with a random variable $X$ defined as number of events in an hours. Further, we assume that $X ...
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1answer
21 views

How does one determine the sample size and statistical analysis to be used?

How does one determine the sample size and statistical analysis to be used for an experiment wherein there will be two interventions (no standard medicine for positive control) A and B, and the ...
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1answer
18 views

Futility analysis sample size

I have been asked to determine the sample size needed to demonstrate futility in a small study. I suggested going the "traditional route" and conducting an interim analysis at a pre-specified ...
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0answers
38 views

Calculation of sample size

I'm doing a comparative study between two warming devices for patients undergoing renal transplant surgery.. patients are divided into two groups and are warmed by the device of that particular ...
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1answer
57 views

Sample size for categorical data

I have a population of phone calls - 200,000. There are different reasons for each call, but lets assume the number of reasons is known. i.e. 7 different call reasons: 1) Check on order 2) Cancel ...
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1answer
53 views

Confusion about the sample distribution.. Can you please enlighten me?

I thought that the sample distribution was an approximation of the distribution of the underlying phenomenon. But then the book says: We will denote the sample size by $n$ ($n \le N$) and the ...
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20 views

Sample Size Computation

I have defended against a group of expert panelist today and they all agreed that Slovin's is not longer accepted as a sample size determinant. I am really not a math genius and somehow goes slightly ...
3
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1answer
124 views

Effect of sample size in F-test?

Having worked hard to understand the t-test, I'm rapidly falling out of love with it. All that is required in the t-test to gain significance is increase sample size, which renders it close to ...
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0answers
34 views

weight of sample sizes in quasi-binomial GLM for proportion data

I'm studying a colonial organism, and my hope is to compare differences in percent survival between three treatment groups. The results are clear, there is a 55% difference in survival between ...
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0answers
23 views

imbalance in sample size at multilevel longitudinal data

I have longitudinal data (BMI level) measured at 3 time points and subjects are students nested to schools. The sample size in school level differs considerably (n=85 % in school 1, n=10 % in school ...
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0answers
28 views

How many samples are enough

I have objects with large number of attributes (about 60.000). Attributes are actually deviations of object part from model. I would like to cluster this objects, to get centroids that will represent ...
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1answer
124 views

Stepwise logistic regression

I am working with a dataset of 1000 individuals, 200 of which are disease positive. I have run a logistic regression with 25 predictors to identify overall which variables are significantly ...
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1answer
37 views

Why should changing the units of the variable change the required sample size?

I am trying to calculate the survey sample size necessary to estimate average rice yield. If the standard deviation is 10 tons, then the variance is 100. Plugging this into the sample size formula ...
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3answers
106 views

Why take multiple samples from a population?

I'm fairly new to Econometrics, and I'm curious about, when trying to estimate the population parameter, why it is important to take multiple samples of the population, instead of just combining all ...