The sample-size tag has no wiki summary.
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0answers
39 views
Measuring the effect of sample size on classification
I've got a data frame with 1000 observations and I am playing with classification methods using caret package. I'm mostly using the bootstrap method to check model ...
2
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1answer
57 views
Sample size with respect to prediction in classification and regression
With respect to hypothesis testing, estimating samples sizes is done through
power, and it is intuitive that increasing the same size increases
the precision of estimated effects. But what about ...
1
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1answer
32 views
Standard errors of regression coefficients based on sample size
For any particular nonlinear regression: $$Y_i = f(\mathbb{x_i},\theta) + \epsilon_i, i=1,...,n$$ I currently have standard errors for each of the $\theta_j$ obtained via the Gauss-Newton algorithm
...
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1answer
46 views
How to add confidence intervals to describe the variability in monthly samples of data?
The data analyzed here is a sample of individuals collected on a monthly basis. What would be the best way to compute "confidence intervals" for the monthly sample means, in order to indicate the ...
2
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0answers
47 views
Determine sample size without knowing standard deviation
I want to calculate the required sample size for a call centre with a finite population.
The survey will collect data on many variables. The objective is to gain data about a range of psychological ...
4
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1answer
82 views
How to test for normality of growth disturbances in chemo treatment?
I'm a med student, conducting a retrospective analysis of weight/growth disturbances during chemo treatment.
I wonder, if I should:
assume, that growth is a variable normally distributed across the ...
2
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1answer
34 views
How to standardise cases within groups to perform ranking across groups and over time?
I am trying to create a method to rank ships according to their fuel burn rates. There are two different classes of ships, with different burn rates, so I am trying to create a mean and standard ...
2
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2answers
72 views
Does the intercept count as a parameter for the n/parameters sample size rule for multiple regression?
When estimating parameters, I know the general rule of thumb is n/parameters should be >10. Does the intercept in a model count as one of the estimated parameters in this "rule"?
For example, if I ...
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0answers
42 views
Types of regression that might work on small samples
I know that this kind of discussion might be both a silly...very silly and a hot issue simultaneously...but I thought it would be nice to raise it : Which types of linear AND non-linear regression ...
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1answer
22 views
How to determine the sample size of a Latin Hypercube sampling?
I am designing an experiment with 5 variables. Some of the variables have 2 and others have 3 levels. The method that I am going to use is the Latin Hypercube, but I do not not what the sample size ...
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1answer
71 views
Interpretation of Spearman correlation for small sample
I am currently being confused by different opinions regarding the spearman correlation interpretation. Some says, $\rho<0.2$ can be ignored as small/weak relationship, some says $\rho<0.1$, for ...
2
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1answer
46 views
Visualise data with different sample sizes
I did a literature review and ended up with a lot of data in the kind of "10 out of 20 studies found x while 4 out of 8 studies found y".
To be more precise; I looked up the contribution of seafood ...
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0answers
59 views
Precision, Recall and area under ROC curve as sample size increases
The following is a question from an exam paper on evaluating the performance of search engines. To this day I looked in my text book and literally close to 50 web pages and I can't
find one convincing ...
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0answers
33 views
Repeated 100x 10-fold cross validation, what is the sample size when doing an significance test?
I iterated my 10-fold cross validation 100 times for several methods. Now I want to use a t-test to test if the results are significant. However, I'm not sure what the sample size is.
Is the sample ...
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1answer
93 views
How to justify the sample size? [closed]
I'm wondering how can I justify my sample size! I have 45 observations and 6 independent variables from which one is control variable. Is there any rule of thumb or specific test in this regard?
Many ...
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0answers
37 views
For bootstrapping, why does a higher subsample size lead to lower variance?
I've been working on a bootstrapping problem that's left me a little confused and wondering whether I'm doing things correctly.
We have around 200 samples from a population of about 3,400, we want to ...
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0answers
84 views
Given a small pilot study, how to compute number of samples needed for a certain power?
I ran a small pilot study and computed both a p-value and Cohen's d. Now how do I compute the number of samples needed for the full study if I want a given power (e.g. 95%).
I hoped I could use this ...
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5answers
1k views
Is the number 20 magic?
I have references that advised to consider a sample size of minimum 20 for data fitting distribution.
Is there any sense in this?
thanks
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0answers
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Tolerance as the probability of success
Often you try to find the number of samples needed (at least a lower bound) to meet a certain level of tolerance $ε$ that is usually given as some sort of absolute value. Generally done like so:
• $n ...
3
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1answer
61 views
How to back-calculate change from baseline from a p-value for a paired t test
I have a result from a study in a research paper which gives a mean/SD for 2 time points (pre & post treatment), and a p-value based on a paired-samples t-test. What I want to calculate is the SD ...
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0answers
22 views
Choosing a Sample Size for a SOM Cluster
Is there an accepted formula to determine a good lower bound for the number of samples needed for the initial input on an SOM clustering algorithm?
For example - If I know that there are X number of ...
0
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0answers
40 views
What is the minimum sample size for discrete choice experiment (DCE)?
I am preparing to conduct a DCE and am unsure on the sample size that will lead to significant results. I will have 3 alternatives with 5 attributes for each. Some will be generic while some will be ...
1
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0answers
47 views
Taking average of linear regression results
Say I have a very large sample of observations, like a thousand of them, and I want to do (multiple) linear regression on them, i.e., regressing the response variable on the predictors. Now instead of ...
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0answers
32 views
Can I improve data accuracy by taking many smaller samples? [closed]
Please excuse my lack of stats knowledge - it's been a while since I took Stats101.
Currently at my workplace we take a single 250g sample from a bin of product to analyse product quality. This ...
4
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1answer
178 views
How do I calculate sample size so I can be confident that the sample mean approximates the population mean?
Unfortunately, it's a long while since I did statistics and despite reading & research I'm not 'confident' as to how to calculate this correctly.
I would like to know the smallest sample size ...
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0answers
24 views
Sample size for Wilson's confidence interval
Consider a story ranking website in which the ranking is crowd sourced from the number of up votes and down votes received by a story.
The score is computed as the lower bound Wilson's algorithm.
...
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1answer
73 views
Compute the variance of parameter estimates given limited number of samples
I'd like to infer the variance of estimated parameter $\hat\theta$ of the density function of $f(x;\theta)$ given only a limited number of samples $X_1,\cdots,X_n$.
Bootstrapping doesn't perform well ...
3
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3answers
247 views
Normality assumption and sample size
I know this is a very debated topic, even on this site, but I still couldn't find an answer to my problem.
Recently I am working with large samples (300, 400 and more). For now, I am trying to use ...
1
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1answer
83 views
(When) Does simulating a larger sample from a small sample yield better results?
I am trying to classify a set of $p$ predictors into 5 classes. But my sample size $n$ is rather small, so I fear I won't get a very robust estimate.
Now an idea would be to subset my data for each ...
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0answers
217 views
G*Power-Repeated measures MANOVA “number of measurements” input field
I am trying to calculate the sample size needed with G*Power for my dissertation study. I will be doing a Repeated Measures MANOVA within/between interaction. My question is in the field "number of ...
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0answers
148 views
Sample size and hypothesis testing problem in linear mixed effect models
I have a dataset about the growth of an aquatic plant in different sites (lakes) and months. In particular I have 3 sites and for each site 3 plots in which the biomass of 3 plants was measured. The ...
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0answers
59 views
Sample size determination crossover study
I would like to have some help with this sample size determination.
This is a 2 ways, 2 period crossover study to evaluate a drug drug interaction
Design:
TR
RT
Parameter to evaluate
AUC ...
3
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2answers
120 views
How does the confidence interval for the parameter p of a bernoulli trial vary with the value of p itself?
This is a very basic question (I'm currently studying undergrad level statistics), but I was hoping for some clarification regarding an assertion I read in a newspaper article earlier today. The ...
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67 views
Sample size calculation for multivariate problems
I am interested in multivariate investigations. I have been trying to learn about designing such experiments where there is one dependent variable (a class/group) and many independent variables that ...
1
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1answer
109 views
How to find Coefficient of Variation with E(X), E(X^2) and sample size?
Given E(X), E(X^2) and sample size. How do I find Coefficient of Variation?
Variance = E(X^2) - E(X)^2
sd = square root of variance
Coefficient of Variation = sd / E(X)
however, with the values ...
1
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0answers
62 views
Sample Size Determination for Rare Event
Suppose a survey contained a dichotomous variable of chief interest, such as smoker/non-smoker, along with ten other dichotomous variables. Then suppose that the incidence of smokers is a rare event ...
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77 views
Sample size power and sensitivity
I'm building a multinomial ordinal logistic regression model in SAS. Here is some description:
I've an ordinal response variable (has 4 levels) and 3 categorical covariates (each one has different ...
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0answers
71 views
Pooling data with unequal sample sizes
I have searched far and wide for a clear answer to my question (and am aware that a clear answer may not exist) and I'm hoping someone might be able to help me:
I have survey data for 4 samples of ...
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2answers
217 views
Mann-Whitney for non-normal distributions with n>20?
I have 12 groups of datasets (mostly non-Normal, quite right-skewed), and I would like to see if there is a significant difference within each pair. (But the data itself is not a paired dataset, as in ...
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44 views
Variable length word sampling problem
I have a unusual sampling problem.
I have a continuously growing file with millions of words in it. Each word can have 1 to 8 characters in them. A word can have duplicate characters in them. The ...
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0answers
51 views
Path analysis of empirically evauluated model and sample size
I am new to the Path Analysis and ESM. I have been doing reading on this method, but still feel very much confused.
I have a empirically evaluated failure model having 45 variables connected with ...
1
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2answers
142 views
Under what circumstances is an N < 30 acceptable?
I am doing some research in which I want to expose subjects to an "unusual" event and record their response. I am recording the subjects' responses via a sensitive brain instrument, so I've been told ...
2
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2answers
318 views
SEM or path analysis using AMOS, issues with sample size and model complexity
I am new to SEM / AMOS and as such I have done a lot of reading around my problem but find I am getting lost, any help would be appreciated and I am sorry if this sounds rather basic;
I have a model ...
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0answers
20 views
Determine likelihood that a list of N items contains no negative results after examining X items
I have a large (N) list of results from a process that is either positive or negative. After examining X of them and receiving only positive results, how certain can I be that the list only contains ...
1
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1answer
44 views
Is there a general rule about max nr of variables to use in (generalized) linear model?
I am running a generalized linear model on a dataset with 19 individuals and have 4 variables of interest. There are furthermore a number of interactions that might be interesting to look at. I was ...
3
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1answer
122 views
Resampling with replacement permutation analysis
My question might be easy for most of you to answer. I am starting to learn statistics and coding in R so my questions are on the basic level.
I have a dataset of (two groups, replicates). My data is ...
4
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1answer
366 views
Power calculations, logistic regression with continuous exposure--cohort
I'm trying to estimate power in a logistic regression with a continuous exposure in a cohort study (ie, the ratio of the sampling probabilities is 1). I have population cumulative incidence ...
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2answers
547 views
Sample size calculation for mixed models
I am wondering if there are any methods for calculating sample size in mixed models? I'm using lmer in R to fit the models (I have random slopes and intercepts).
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1answer
75 views
The use of effect size
I was able to calculate the sample size using two different effect sizes 0.3 and 0.5 and each gave me different sample sizes. 0.3 gave me 82 and 0.5 gave me 26. I have 45 students in that gradelevel. ...
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1answer
212 views
How do I use student's-t distribution without the sample size?
Here is my question (homework obviously):
A sample from a normal population produced variance 4.0.
Find the size of the sample if the sample mean deviates from the population
mean by no more than 2.0 ...
