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This tag is very ambiguous. Use it when the question is about sample size and NONE of the following are more appropriate: [small-sample], [large-data], [power-analysis], [power], [underdetermined] or [unbalanced-classes].

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Appropriate regression method for N=28 and T=260 data? [on hold]

I have N=28 AND T=260 weekly data and I want to check impact of two variables on stock volatility. I proposed that one variable moderates the other's effect on stock volatility. I was using time ...
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Long T Small N causal time series ols regression analysis ? can i use panel data? [on hold]

I have N=28 AND T=260 WEEKLY DATA and i want to check impact of two variables on stock volatility.i proposed that one variable moderates others effect on stock volatility . I was using time series ...
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12 views

How to calculate sample size for study design where observations are nested in study site?

I need to estimate the required sample size for a future study with a nested design and thus, mixed effect regression. Sampling will take place at six plots per study site and observations will thus,...
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10 views

Determine sample size in power analysis

I have several confusions regarding estimating sample size. Consider the situation where I have data from a pilot, from which I estimated effect size and want to do power analysis (using software such ...
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7 views

Calculating sample size required for proving equivalence or superiority to population?

I am trying to determine sample size for a new approach to cancer detection such that the approach can be considered equivalent or superior to average population statistics. In my case, I assume that ...
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12 views

Are my statistically significant results invalid if I fail to reach my desired sample size?

I conducted an unfunded study where 3 groups of 15 participants were observed over 11 timepoints. There were statistically significant between-group differences in slope and also statistically ...
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10 views

How to find the best representative sample for performing sentiment analysis on a large collection of texts

I'm trying to perform a sentiment analysis on a collection of reviews from Amazon. The dataset is about 500,000 rows and it's taking forever to preprocess the data. I'm considering taking a random ...
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16 views

Comparing averages of unequal population sizes

Imagine the following problem: I have 1000 plots of land. On each plot of land I plant 1000 Oak trees and 1 Elm tree. Each plot of land differs in multiple parameters (e.g. sunlight, soil type, ...
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22 views

Logistic Regression Box Tidwell Large Sample

I am doing a logistic regression (binary DV) with 13 IV. As a first step I wanted to test the linearity assumption bw. the IVs and the logit. To do this I applied the Box Tidwell Method in SPSS by ...
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14 views

Standardized vs absolute effect size in repeated measures ANOVA

There is 3 repeated measurements in 100 subjects. I would like to determine if 100 subjects is sufficient to determine the absolute difference of 5 units between the repeated measurements. Software ...
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1answer
23 views

How large sample size for defining difficulty

I am currently making a website in which you can get several trivia questions. One thing I would like to implement is difficulty of questions. However, you can't just take a question and decide for ...
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6 views

Small sample size for partitioning and evaluating a CART

I have a data set of 130 samples. If I partition the data 70/30 % to run a conditional tree, CART, and then evaluate it, the results are different than if I run the 100% of my data in the CART. When I ...
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1answer
25 views

Detecting significant effects based on critical t value for a given sample size

"Because (this study) collected 77 participants in total, and used an alpha level of .05, the critical t-value is 1.99. This critical t-value can be transformed into a 'critical standardized effect ...
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17 views

Determine sample size of beta distribution to detect a difference in means to a second beta distribution for a particular confidence level.

I try to understand how a former colleague of mine came up with the answer to the following question. We have two Beta distributions with the first one having $µ_1$ = 0.2, $\sigma_1 \approx 0.02$ ...
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16 views

Conducting a Pilot Study without Large Sample

I want to obtain preliminary evidence that some experimental manipulations I would like to use in research have a good chance of being successful (i.e., successfully manipulating the intended ...
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12 views

Sample size for comparing two properties of time series data

I have a dataset of observations of two properties of an object (x and y), which are distributed over time, ...
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1answer
27 views

RM one-way ANOVA or Friedman test

I here my question. I'm testing with n=6 animals in 6 different situations. It's repeated measures because all 6 animals did the same tests. When I do the column statistics to see if the distribution ...
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8 views

Weak Sample Size & Low Statistical Power

I have a problem of sample size for my research paper approval. I could only ran the statistics on 5 subjects for both plantar pressure and temperature measurements but the statistical power seems to ...
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8 views

Sample Size for categorising of Dataset with multiple categories

I am looking through a dataset of 17,200 records over 3 years categorising into 1 of 31 different categories these will not be evenly distributed in fact chances are the top 5ish are likely to be far ...
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1answer
27 views

Sample size calculation for 3 groups?

I want to determine the sample size necessary in a study of 3 different treatment groups using a one-way ANOVA. The clinically significant difference here is +/- 10. When entering means into a ...
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Can I sample 500 out of 10,000 using bootstrap for variable selection?

I have a population dataset that has more than 10,000 subjects. When I used LASSO regression for variable/feature selection it did not work as almost everything was statistically significant because ...
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1answer
16 views

Calculate critical test value required for statistical significance given sample size and alpha/

How does one calculate the critical t value that will satisfy statistical significance for a given alpha level (.05), statistical test (e.g., paired t test) and sample size? And how does one transform ...
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42 views

How to decide how many age bins to use?

I'm planning an analysis using ANOVA and would like to group participants into age groups to see if there is a difference in test score between age groups. I have n=20,000 and the age ranges from 20-...
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16 views

Sample size - Before/After Study - percentage variation

I need to calculate the sample size required for a Before/After Study with an Intervention group and a placebo group (ratio 2:1). The variables are continuous and are supposed to be normally ...
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1answer
38 views

Sample size for a research paper (for Mean+SD type of data)

In my research paper I proposed a software and have experiment it on 72 users. But the reviewer has objected on the sample size and asked to justify it or increase it. below is the results of our ...
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21 views

Method to determine the required sample size: distance or number?

I'm working on a problem that requires me to carry out a survey of the condition of 5000 footpaths which cover total distance of 2573 km. The condition outcomes are either 'Pass' or 'Fail'. I only ...
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17 views

Determining Sample size of Unknown Population Standard Deviation

I am trying to determine the sample size for 95% confidence interval. I am a bit confused how to compute the sampling error. My proportion of events of interest is 0.45. The Z-value will be 1.96 but I ...
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14 views

Sample Size based on Variables Used

I have survey data that collected responses for a number of variables. I'm wondering, what are the best practices for dealing with missing data in this context? To illustrate my question, consider ...
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1answer
38 views

12 independent samples are “enough” in MCMC sampling for what?

I'm reading Learning in Graphical Models (Jordan 1998) and in the chapter Introduction to MCMC method by D. J. C. Mackay (page 201) it says this: It's not clear to me to what this is referring to. "...
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1answer
22 views

Why is the sample size calculation not in agreement with t-test results?

I used R package pwr (G*Power gives the same result) which say for a one-sided t-test of means with alpha=.05, beta=.20, that I would need 40 samples for both control and treatment groups (n=80) to ...
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30 views

Why there is no agrement on power / sample size for factorial repeated measures design?

I'm not really sure to what degree this is a statistical question but thought this might be the best place to start. If my questions prove only my ignorance please vote it down and I'll delete the ...
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15 views

Need Help Calculating Sample Size For Logisitic Regression on G Power

I am conducting a study with 2 continuous independent variables and a binary dependent variable. On G Power, I was able to find the logistic regression option but do not see where I enter/account for ...
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1answer
15 views

Need help determining sample size for logistic regression [duplicate]

I need help determining the sample size necessary for a logistic regression (binary DV) with two continuous predictors and also the sample size necessary if I use three continuous predictors.
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1answer
52 views

Multivariate statistics sampling and standard error problem

I have a group of workers listening to audio from many various audio files and typing it out. I want to compare the average transcription accuracy of these old workers with 2 new workers. I have a ...
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confusion about the link between residuals, error terms, sample size and CLT in ANOVA

I feel a little confused about the assumption of the ANOVA and what it ensures mathematically the errors have to be iid and normally distributed N(0,1). independance of observation. Is it not a ...
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Hello, I would like to know how to calculate the sample size of a stratified randomization design.

We will obtain information about the individuals height, weight and age. Once this information is acquired, we will create matches within our data so that the height/weight/age from a given ...
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21 views

Multivariate hypothesis testing for proportions

It's very common in website optimisation to run A/B tests for conversion rates (e.g. 'buy' button is green by default, would the conversion rate from 'visit' to 'buy' be significantly larger if we ...
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11 views

Discount testing for retail chain

For a retail chain I want to measure the effect of running new discount promotions for 5 to 10 items. In total there are 700+ stores in various sizes and locations. I want to give 100 stores a new ...
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43 views

Determine sample size for three-way ANOVA with repeated measures

My experimental Design looks something like this: two groups do a Simon task. There's four dependent measures for every subject: Reaction times to congruent vs. incongruent trials in n after a ...
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1answer
20 views

Analyzing reviews with different sample sizes

I am trying to analyze restaurant ratings and comparing it by the different cuisines. The problem is my data set has uneven sample sizes (6 Greek rest., 100 Indian, 50 Lebanese, etc.). How can I take ...
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1answer
45 views

What explains a sudden change in the magnitude of logistic regression coefficients when increasing the sample size

Last week my team and I discovered a strange phenomenon with the coefficients of a logistic regression (LR). As we included more samples from a static dataset, the magnitude of the coefficients of the ...
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1answer
17 views

Sample size for designing a study which creates a classifier

I have to plan a study in which I will have to create a classifier. The output variable is a binary with an estimated proportion of value 1 in the overall population of interest to be 0.10 (and ...
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19 views

Is having cumulative samples a problem?

We are running a marketing campaign where we send out comminications to a select group of customers on daily basis. The customers are different each day. However each day we only have a small number ...
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why is it desirable to have fewer explanatory variables in the second stage of a Heckman test?

My old lecturer recommended that the second stage of a henchman test should preferably contain at least one fewer explanatory variables than the first (selection) stage. what is the precise reasoning ...
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Average sample size from combined correlations in fishers z [duplicate]

I have combined several correlations into fishers z scores for meta analysis. Most of the combined correlations are measuring the same construct within the same study. I now need to calculate the ...
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232 views

Sample sizes without significance levels

I would like to know about a strategy for estimating sample sizes when you're not concerned with statistical significance hypothesis testing (e.g. along the lines in Abandon statistical signficance - ...
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11 views

Taking into account uncertainty in future values of $S^2$ with continued sampling

This will be a variation on the theme of this question. Suppose you take a sample of small size $n$ from a normally distributed population and you get the Bessel-corrected $S^2= 2.5^2.$ Where I say "...
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1answer
26 views

Implications of sample size increasing over time

I have apartment data on rents from 2000 to 2016 where the unit of observation is an individual property. The sampling methodology included more properties as time went on thereby expanding the ...
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9 views

Difference in size sample between nominal and ordinal logistic regression

For linear regression, I understand that there is a 1 in 10 rule. For example, if I have a continuous dependent variable and 100 observations then at most I could add 10 binary or continuous ...
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33 views

Sample size and significance

I conducted a series of multiple linear regression analysis to estimate the effect of a treatment. The sample size variates from 100 to 500, while about 10 covariates are included. Since I had no ...