sample size calculation

  1. A

    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...
  2. C

    Sample size estimation for evaluation of diagnostic tests

    I am studying 2 blood tests (A and B) to detect infection following exploratory laparotomy undertaken to treat various surgical lesions. In other words, the population is somewhat heterogenous. In a similar previous study (51 patients), other authors reported on test A. The blood will be sampled...
  3. E

    Sample size, effect size and power.

    Hi all, I have a question I haven't been able to answer. I hope you can help me :). I use G power to estimate sample size. In my case, the estimated sample size for my desired effect size = 0.25 and power = 0,95, is 400. But the estimated sample size for an effect size = 0.5 and power = 0,95...
  4. P

    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...
  5. J

    Sample Size for Variable Data

    Hello, I am trying to determine whether or not our sample size criteria is correct. Some time in the past, my company adopted a standard practice document that lines out sample sizes based on certain criteria, i.e. variable vs. attribute, critical to quality vs. non, software, etc. My question...
  6. S

    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.
  7. T

    Adequate subsample size to represent sample regression

    I am performing an engineering analysis to find out the effect of earthquake on concrete buildings. Analysis applies earthquake forces on building model for 50 earthquakes, resulting into separate 50 analyses. Earthquake intensity is independent variable of study. building drift, extracted from...
  8. S

    Design help

    Design help
  9. R

    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/...
  10. E

    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...
  11. D

    Sample size calculation

    I have a normal distribution: log(xi/yi) ~N (0, c^2/yi). I need to work on the posterior distribution of c^2. I know c^2 follows a gamma distribution. I need to know what sample size I need to estimate the c^2?
  12. S

    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...
  13. B

    Sample size in a lot with clumped error

    Hi, A big bag is emptied in X amount of smaller bags. We are trying to detect an error which is clumped. In other words, if an error is detected into 1 of the X we are sure all the other small bags with errors are grouped around that initial sample. Is a sample size described in the following...
  14. C

    Sample Size Calculator (one group versus population)

    Dear all, so far I couldn´t find a solution to calculate the required sample size for the following scenario: Goal: Research continuous variables (cost perceptions) of a population through one sample group. --> means of one group need to be significant for the entire population...
  15. T

    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...
  16. E

    Help for sample size calculation

    in my prospective cohort study I will assess the serum level of a vitamin in a group of patients the normal reference serum range is 10-30 in normal population there is no control group then i will correlate the serum level with later occurrence of outcome (yes or no) So I need to...
  17. G

    Parallel Bioequivalence Study Sample Size

    I need to calculate the required sample size given the following information: Power=80% Coefficient of variation for Cmax and AUC = 40% True ratio of the geometric means=0.95(1.05) Probability that the 90% CI of the ratio falls into the range 0.80 to 1.25 is 80% In addition, we...
  18. M

    I do not know how to calculate my sample size…

    Hello, can someone help me calculate my sample size and showing me the steps of how it should be done? I am going to do a study to see a linkage between genotypic resistance and suppression of HIV. When taking the some HIV drug, some people are able to suppress the HIV virus and some people...
  19. S

    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...
  20. W

    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...