The sample-size tag has no wiki summary.
3
votes
1answer
72 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 ...
1
vote
1answer
25 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
...
0
votes
0answers
19 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 ...
1
vote
2answers
98 views
Comparing patient and control group results of a survey
I have data from a survey given to a patient group and control group. Both groups completed the same exact survey (Likert scale). One group has an n of only 5 or 6, the other n was about 15.
What ...
2
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0answers
38 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 ...
2
votes
1answer
33 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 ...
23
votes
5answers
13k views
Rules of thumb for minimum sample size for multiple regression
Within the context of a research proposal in the social sciences, I was asked the following question:
I have always gone by 100 + m (where m
is the number of predictors) when
determining ...
2
votes
2answers
71 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 ...
1
vote
1answer
70 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 ...
2
votes
1answer
19 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 ...
0
votes
0answers
41 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 ...
-1
votes
1answer
405 views
Question regarding sampling, estimation and accuracy [closed]
Let's say there are N chunks of metal, each are 4 inches thick. They are to be hammered and reduced to following best possible sizes: 1, 2, 3 or 4 inches. If we were to use sampling to get an estimate ...
0
votes
1answer
181 views
How does confidence interval vary with sample size?
I am trying to convert state-level poll results for 2012 U.S. presidential election into state-level probabilities of each candidate winning. To achieve that, I am using the logistic function, which ...
1
vote
1answer
244 views
Predicting dependent variables where independent variables are samples with differing sample size
Is there a standard method of dealing with independent variables, where they are samples from a known distribution, and the sample sizes differ from sample to sample?
I'll give an example of what I ...
3
votes
1answer
59 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 ...
0
votes
1answer
68 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
votes
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 ...
3
votes
3answers
231 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
vote
1answer
147 views
Comparing the result of a study which has unequal group sizes
I have conducted two user studies and in my studies I didn't have control over the group sizes. In each study users were put in groups and they were asked to perform some group activities. Here is the ...
1
vote
0answers
58 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 ...
-2
votes
1answer
88 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 ...
0
votes
0answers
31 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 ...
3
votes
1answer
353 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 ...
2
votes
0answers
83 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 ...
0
votes
1answer
134 views
How to calculate sample size needed for comparing the “change from baseline” scores between two groups?
I'd like to know how to calculate the sample size needed for comparing the "change from baseline" scores between two groups?
Thank you in advance for your consideration
0
votes
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 ...
11
votes
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
0
votes
0answers
17 views
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 ...
1
vote
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
votes
0answers
39 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
vote
0answers
45 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 ...
2
votes
2answers
309 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 ...
10
votes
2answers
581 views
Complications of having a very small sample in a structural equation model
I am running a structural equation model (SEM) in Amos 18. I was looking for 100 participants for my experiment (used loosely), which was deemed to be probably not enough to conduct successful SEM. ...
4
votes
1answer
369 views
Minimum sample size to achieve a specific confidence level and interval
I am building software components that are going to be used by multiple users
simultaneously. At the current point in time, these components are known
bad. That is, if I simulate multiple users ...
4
votes
1answer
174 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 ...
0
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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 ...
0
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0answers
21 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.
...
0
votes
1answer
561 views
Minimum population size for chi-square test?
I'm analyzing data from an experiment in which two independent groups were exposed to an experimental setup without and with treatment.
I am testing whether treatment changed the second group's ...
13
votes
2answers
301 views
What is the relationship between sample size and the influence of prior on posterior?
If we have a small sample size, will the prior distribution influence the posterior distribution a lot?
1
vote
1answer
82 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 ...
0
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0answers
143 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 ...
1
vote
0answers
210 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 ...
0
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0answers
64 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 ...
0
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0answers
58 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
votes
2answers
119 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 ...
1
vote
1answer
104 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 ...
4
votes
2answers
123 views
For “Was this page helpful” data, should I take response rate into account?
To help me focus on which pages on a site to improve, I'm looking at user feedback to the question "Was this page helpful?" (Answers are "Yes" or "No".)
The response rate (responses divided by unique ...
0
votes
1answer
199 views
Optimal sample size for panel data
Is there a way to calculate the optimal sample size for a balanced panel over 8 years from a population of approximately 30,000 and involving 10 variables being studied, say for 95% degree of ...
1
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0answers
59 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 ...
0
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0answers
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 ...
