# sample size determination

1. ### Sample size calculation for survival clinical trial

Hi! I need to calculate sample size for phase 3 clinical trila with following assumption: Primary Endpoint: Overall Survival (OS) in 36 months; Study Hypothesis: superiority (H0: Υ ≥ δ; H1: Υ < δ); Type I error: 2.5% (α = 0.025); Type II error: 20% (β = 0.2); Expected HR for...
2. ### Random Sampling strategy for multiple populations

I have the following situation: 6,000 letters created in July 250 staff created the letters Some staff created more letters than others I'm looking to do a quality assurance exercise where we check the quality of a sample of the letters created by the staff. I need some help to understand...
3. ### DCE Sample Size calculation

I am about to use this formula for a Discrete Choice experiment with 4 attributes each contains 3 Level. Thus, I have some question that I am cordially requesting to get an answer for : - How to fixe the true proportion p as the the true choice proportion of the relevant population? - What...
4. ### Calculate required sample size

Hello, I have a test for the thermal performance of a building with a defined uncertainty margin (15%). I want to use it to measure the effects of refurbishments designed to improve thermal performance, but the effect of the refurbishments can be quite small (5-50%). In order to have confidence...
5. ### Sample Size calculation - "difference in mean differences"

We have two independent patient groups in an Individual RCT ("treatment" and control["standard care"]). The treatments will result in a change of scores on a psychometric scale, from baseline to end-line. A baseline assessment was conducted using this scale, and thereafter, the participants were...
6. ### Is there any method to determine the size of the subgroup used in the Kolmogrov-Smirnov test?

Hi everybody, I have a data set of 5000 sample. I want to apply the K-S test on subgroups of this data set to check if two consecutive subgroups are derived from the same population. I am confused about the size of the subgroup to be used. Does anyone know how to determine/estimate that size...
7. ### Mechanical Engineering Sample Test Size

You need to conduct an engineering 3-Point Bending. How many samples should you test? I was recently asked this in an interview but was not sure how to answer. I tried saying that it would depend on time, the readiness of the samples, and the cost of the tests but the interviewer said to...
8. ### Sample size for observational study

Hi everyone! I should to calculate sample size for observational study in that the primary endpoint is to assess the distribution of COPD by 4 classess (COLD). According to article i know expected distribution by class: 1 class: 16% 2 class: 25% 3 class: 28% 4 class: 31% How I may to estimate...
9. ### Sample size calculation for cohort study

How to calculate sample size for cohort feasibility study? I use the online tool: http://clincalc.com/Stats/SampleSize.aspx Any other options available? Please suggest.
10. ### Standard error calculation for more than one sample size

Hi all I am conducting a meta analysis of pearsons r correlations. Whenever a study has presented more than one correlation I have averaged them into one correlation by converting them into fishers z scores. I now have the problem that I need to calculate a standard error and variance of the...
11. ### AB Test with Proportions

I'm trying to design an AB test for proportions, and I need to understand the minimum sample size I need to get a statistically significant result within a 5-10% change of a very small proportion. This calculator summarizes the type of test I'm trying to set up: https://abtestguide.com/calc/...
12. ### Engineering Research, starting to look at statistics

Hey everyone, This will be my first post on this forum. I'm an engineering grad student and I have a little experience with statistics,but not enough to be able to do a sound analysis. I've completed my system design and will start looking at data collection. My primary aim is looking at...
13. ### Determining sample size from confidence interval and significance level

Hi everyone, I am studying a university level stats course at the moment and I have been given some excerises to take home that I am struggling with. I am asked to calculate sample size for a hypothesis that requires an 90% probability of detecting a difference at a significance threshold of...
14. ### Sample size calculation for a one way anova (three conditions)??

Hi there, I am designing a study that compares three conditions (differences in glass shape) on one main DV (drinking rate) (as well as some secondary DVs). I want an adequate sample size to be powerful enough to test the primary hypothesis, that there will be a difference between the three...
15. ### Appropriate sample size for unusual "populations"

There seems to be a lot of literature about determining sample size based on population, margin of error and confidence level. This seems difficult to apply to surveys where the "population" consists of large institutions. For example, say it's a survey on investment allocation by public...
16. ### Best way to calculate power, precision & sample size using complex pilot data set?

I have a large and complex pilot data set of electromyographic (EMG) data collected from human subjects performing several different exercises. A single subject was used for all data collection in this pilot experiment. Each data set involves one particular exercise being performed with one...
17. ### Clinical Trial - sample size for statistically comparable data?

Hi Everyone In a nutshell - I am looking to undertake an 8 week clinical trial of an equine veterinary health product. I am wanting to analyse corticosteroid concentrations deposited in the keratin of mane hair at Day 1 and then Day 56. I was hoping that 20 horses would be a sufficient...
18. ### Clinical Trial - sample size for statistically comparable data?

Hi Everyone In a nutshell - I am looking to undertake an 8 week clinical trial of an equine veterinary health product. I am wanting to analyse corticosteroid concentrations deposited in the keratin of mane hair at Day 1 and then Day 56. I was hoping that 20 horses would be a sufficient...
19. ### How to select the training dataset

I have a dataset which contains dependent variance Y and several independent variances X1, ... , X10. Y has 5 possible values: A, B, C, D, E, a proportion of each value is: A: 80%, B:10%, C:5%, D:3%, E:2%. I want to build a model to predict the value of Y, I decide to pick up 70% of the...
20. ### Min sample size for Wilcoxon Rank Sum test

Hi, I have data measurements (eg, running cost) that keep coming in to the system continuously. There are two groups (say X and Y) that I want to compare. I want to see which one is systematically larger (H1: X > Y?). However, I have a couple of issue with my data: i) I can't assume normality...