sample size calculation

  1. 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...
  2. 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...
  3. 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...
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    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...
  5. 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...
  6. 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...
  7. 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...
  8. 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...
  9. D

    How to calculate sample size and effect size for comparing means from two groups

    Hi all, hoping i can find some answers here for a bit of a problem i am having regarding a sample size calculation for a study I am soon to conduct. The population size is 64 and fixed. 32 control and 32 intervention. No drop outs will occur in this trial. There will be a pre (baseline) test...
  10. C

    Estimating Multilevel Logistic Regression Models

    The following multilevel logistic model with one explanatory variable at level 1 (individual level) and one explanatory variable at level 2 (group level) : \text{logit}(p_{ij})=\pi_{0j}+\pi_{1j}x_{ij}\ldots (1) \pi_{0j}=\gamma_{00}+\gamma_{01}z_j+u_{0j}\ldots (2)...
  11. M

    Unusual Power and sample size problem with correlated data

    Is there a way to estimate ‘effective sample size’ based upon data acquired where a correlation quirk of the original data set violated the ‘independence’ of the gathered data points within each group. Here is a description: I have two ovens to create parts/samples in; Oven A and Oven B...
  12. G

    Calculating sample size

    Hello, I am going to conduct a research and would like to estimate the sample size that I will need. Here is the information that I have, please let me know if you need some more information. Thanks in advance. We know from previous research that the probability of phenomena in one group...
  13. A

    power analysis- interpreting sample size given established literature

    Hello and thank you for clicking, I am attempting to use relevant effects size from a published study to obtain a suggested sample size for my related study in G*power. However, 1) the previous study only compared 2 groups w/ t-test and I want to compare 5 with one way ANOVA and 2) the...
  14. M

    When do sample size calculations need to adjust for clustering?

    I am aware that sample size calculations for cluster RCTs must adjust for clustered data. I would like to understand better if such adjustment might be necessary for other study designs. For instance, I am working on a nested case-control study to identify clinical and socio-demographic factors...
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    Sample size calculation for multiple regression

    Hi all! I am struggling with sample size calculations at the minute. I have looked everywhere but all I get is formulas. I have downloaded MedCalc which gives me a number of participants I need per correlation. My supervisor keeps confusing me because she says that it is a different number...
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    Minimum Sample Size Required

    I am a total novice...I do hope you can help! 100,000 people usually shop in Store X. But, only 50,000 people shopped in Store X in Period Y. 10,000 people (of the 50,000) purchased Product Y. Purchase Rate = 20%. How confident am I in the results? And, what minimum sample size did I need in...
  17. P

    biostatistics - sampling size

    Hi. I am interested in discovering motifs in a set of DNA sequence(say 100) and I would like to use the approach of using a subgroup(say 10 from 100) and likewise create random subgroups(picking 10 from 100 randomly) to discover the motifs in the given set of DNA sequences. I would like to know...
  18. T

    Sample size sensitivity in time series regression analysis

    I have a time series that I've built a regression on, say Y = X + Y. For a data set of size 300, the coefficients of X and Y are statistically significant. But, the coefficients are not statistically significant for a (sequential) subset of the dataset of, say, 150 points. Now, since the...
  19. E

    Sample size calculation issues

    Hello, I have a question regarding a research project I'm working on. We have conducted an experiment where the same sample is measured over and over again to get an idea of the analytic variation in our system. We have a nice normally distributed data-set with all parameter estimates. We...
  20. S

    Sample Size in AB Testing

    Hi All, I'm a marketer trying to understand the math behind A/B testing. I understand how to calculate sample size before a test is run. I've just come across a tool that estimates how many more samples are required to reach significance for a test that's underway. Visitors Goals...