sample size calculation

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    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...
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    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...
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    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...
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    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...
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    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...
  7. 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...
  8. 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...
  9. 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...
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    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...
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    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...
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    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)...
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    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...
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    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...
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    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...
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    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...
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    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...
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    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...