# Questions tagged [sample-size]

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

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### what are the implications of incorporating new data and removing old data from a sample set of fixed size?

I have a device that takes sensor readings every 15 seconds. When the sample size reaches 10,001 the device deletes the oldest reading. Thus keeping the sample size at 10,000. Analysis of the data ...
1 vote
26 views

### Sample size justification for single group to get estimate of mean to desired accuracy

I have a sample of computer components These computer components are made in batches (1 batch = 1 lot) of 200 Component components can be individually tested electronically The result of this test is ...
6 views

### Adjusting equivalence sample size for study is self controlled [closed]

I am trying to get a sample size calculation for a DDI protocol where we are looking to test a bioequivalence hypothesis. I am using the FARTSSIE sheet, but I am worried that I am overestimating my ...
1 vote
22 views

### Power calculations based on a subgroup

I'm designing an RCT looking at the effect of a dietary supplement on blood pressure. The nature of the supplement is that it is appealing to both normotensive and hypertensive individuals, therefore, ...
1 vote
38 views

### Rule of Thumb for Mixed Model

Suppose that we have $n$ observations of $(X,Y)$ pair, where $X$ are real (might be vectors), and $Y$ is real. We want to a linear model. One rule of thumb is that the number of learnable parameters ...
39 views

### Sample Size: Cluster Randomized Trials [closed]

I seek a peer check on my approach in calculating the sample size for pair-matched or stratified cluster randomized trials assuming 80% power. Some background on the study: I am working with ...
1 vote
37 views

### Taking longer sample should not reduce the variance of the mean

I have not realized completely why $n$ times longer samples should give you $n$ times shorter variance. However, I measure performance of my programs and there are some fluctuation due to PC state ...
17 views

### Precision-based calculation of mean change

I have two basic questions about SS calculation arounf the mean change, precision based )I'm a physician not biostatistician so sorry if questions are like extremely basic): A colleague of mine ...
1 vote
30 views

### Discrepancy of a sample on Latin Hypercube Sampling

I'm currently working on Design of Experiments (DoE) in order to obtain data to, later on, make some FEM simulations. The starting point is: we want to make those simulations (that depends on some ...
225 views

### Sample Size Estimation for Two Sample T-Test (Excel)

I'm trying to work out how to calculate the necessary sample size for a two sample t-test using excel and need some help. I don't think I am able to upload an excel attachment, so I will write out ...
506 views

### One-tail versus two-tail z-score

In calculating minimum sample size one must specify, inter alia, z-score. I am estimating a min sample size for an accuracy rate. As I only care if the accuracy rate is lower (happy if it is higher) ...
1 vote
23 views

### Assessing the Implementation and Performance of a New Biomarker in Cancer Surveillance

In a surveillance program designed to detect a specific type of cancer in a high-risk population, both biomarker A and ultrasound (US) are used semi-annually. If either A or US returns a positive ...
2k views

### How to run simulation in R to assess sample size and power for SEM?

Muthén & Muthén offer a MPLUS based syntax for calculating sample size and power on SEM, using a Monte Carlo simulation. https://www.statmodel.com/download/FinalSEMsingle.pdf Is there any ...
1 vote
37 views

### How to calculate required sample size for desired false negative rate

I'm trying to design a system that does some binary classification. The cost of a false negative is high, so I want to ensure that I've tested thoroughly enough to minimize this chance. I would like ...
1 vote
304 views

### paired t-test, re: sample size calculation

We are performing a clinical intervention, that we believe will significantly improve some parameters in patients. We expect that the intervention will be successful 85% of the time (it will either be ...
403 views

### Binomial distribution - $n$ for an "at least" Probability

Question: In a binomial distribution for $p=0.48, q=1-p=0.52$, find the population size $n_1$ so that $P(X>=3)=0.95$. My solution : $P(X\geq3)=0.95$ can be rewritten as P(X=0)+P(X=1)+P(X=2)=....
324 views

### choosing sample size in prevalence study with a finite population

I am looking to conduct an epidemiological study on a population of 1000 individuals and need to find the appropriate sample size. So far, I have the parameters to calculate my sample size but I am a ...
53 views

### Sample size calculation clinical trial

I am trying to replicate a study about a randomized clinical trial. For this purpose I want to obtain the sample size calculation the authors did. In the paper they say: Assuming a reduction of the ...
1 vote
34 views

### Considering 96 observation for estimating the intercept (rule of thumb)

I remember Prof. Frank Harrell stated that in order to calculate the sample size using the rule of thumb, we must include 96 observations for just computing the intercept, hence the estimated sample ...
1 vote
114 views

### How to do a power analysis on density (count/area) data?

I would like to calculate the power to detect a hypothetical x% decrease from a mean value, but have a few qualifying questions. The data are strictly positive, right-skewed, continuous data ...
1 vote
2k views

### Sample size calculation for Mixed, Within-between ANOVA

I'm wondering if there is any formula for finding the sample size of mixed, within-between ANOVA. I have tried running it in Gpower but I would like to know which formula Gpower uses to calculate the ...
414 views

### Is it valid to do a mixed ANOVA with one within and one between subjects factor when the between subjects grouping factor has very unequal groups?

I am doing a mixed ANOVA in SPSS where I am currently comparing the duration of certain script handwriting in 2 conditions (1=eyes open and 2=eyes closed) for the same 40 participants in both ...
114 views

### Small-sample binary logit and linear models - response to referees [closed]

Background: This cross-sectional study collected 30 thrombosis samples. We evaluated the presence or absence of MP components (dependent variable), where 24 cases had MP (coded as 1) and 6 cases did ...
1 vote
24 views

### Two-Way repeated measures ANOVA with multiple data points per measurement

I would like to perform a study with physicians of three levels of experience. They shall perform a task under three different conditions. For each condition, the task is performed multiple times (e.g....
15 views

### Group Sample size

I have a group of n items that should ideally be homogeneous, although there may be some variability. I need to determine how many items I should sample and test to validate the entire group. I assume ...
39 views

### Selection of reasonable Power and Alpha for Sample Size calculation

I'm performing an A-B test which involves response rates to communications sent out to customers. I'm looking to calculate a required sample size, and I don't know the expected response rate of the ...
1 vote
210 views

### How to calculate sample size from hazard ratio?

The marker gene XYX1 being high in breast cancer is associated with poor prognosis with higher hazard ratio : 3.5. I want to calculate sample size with 1 - β (power) = 80%, one sided, type I error? ...
1 vote
31 views

### How to know what sample size (number of cells) is sufficient to determine what percentage of cells are above a threshold?

I have a samples with different cell types (one cell type is shown above). I have calculated for each sample and cell type a threshold signifying non proliferating vs proliferating cells. Cells above ...
28 views

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### Sample size. Paired T-Test and repeatability

The study involves 10 subjects, in which we measure speed with 4 different shoes, and the measurements are repeated 4 times, and this is done on two different tracks, indoor and outdoor. On the one ...
27 views

### Sample size for a vector of proportions and simulation

Currently, there are more than 10 variants of omicron virus. Say, variant proportions are X1=0.1, X2=0.35, X3=0.15, etc. I need to calculate the number of samples needed to detect the proportion of ...