sample size

  1. T

    please help me justify sample size for a pilot clinical trial

    I'm a bit desperate for statistical help so trying out all avenues. Any guidance appreciated! I need to justify a sample size of 30 or 32 (15 or 16 per arm) for a placebo-controlled pilot clinical trial of a drug. This is all I can afford, but that is not a good enough justification for...
  2. T

    how to justify a sample size for an underpowered pilot study

    moved to biostatics: how to justify a sample size for an underpowered pilot study UPDATE: I reposted this in the biostatistics forum. I also added some more details, mainly my not-fully-formed thoughts about how to proceed. Thanks! I need to justify a sample size of 30 or 32 (15 or 16 per...
  3. B

    Power analysis and sample size

    Hello all, I've used perused this site numerous times in the past for assistance with statistical issues, but this is my first post. I work with fish, and am specifically interested in the environmental effects on these fish. I ran regressions of growth increment (growth experienced in a...
  4. K

    Sample size calculation for cross-sectional survey (2 Time points)

    I am working on a study design for a study to determine behaviors and structural barriers to health seeking at baseline for HIV negative young women 15-19 years, conduct interventions for 2 years and later study their behavioral changes and remaining structural barriers after intervention. This...
  5. R

    Calculation of Sample Size for one-way ANOVA

    Hello, I have problem of calculating sample size for one-way ANOVA. My settings is the following: Population size = 100 Controlled group = 1 group Treatment group = 2 groups Power = 0.8 Alpha = 0.05 Group allocation ratio: All groups have the same sample size standard deviation of...
  6. S

    Calculation population size and analysis of a study comparing two outcomes

    Calculation sample size and analysis of a study comparing two outcomes Hi i'm having difficulty finding an answer to this specific problem. I'm preparing a pilot study comparing two medical devices. Each device reads a patient's physiological / laboratory data and provides a...
  7. S

    What would you do?

    Hello everybody, I hope this is the right place. I am writing my thesis on Sport industry and I'm currently facing a statistical issue (of course, you'd say, we are in a statistics forum:)). I have to demonstrate the independence between revenues and results on the pitch (represented...
  8. D

    Sample size - have searched high and low,bu tprobarbly very quick and easy to answer!

    Hello Friends, I haven’t looked at a statistics book for a good 5 years, since leaving uni and moving into the job world. However, I have come across a real world problem where I feel there is a statistical method to help me, but after searching high and low cannot find it. I’ve looked at...
  9. C

    Are Unbiasedness and Accuracy of the estimates, all to determine the sample size?

    For determining sample size , why is to focus on the unbiasedness and accuracy of the estimates ? Are this two properties, unbiasedness and accuracy of the estimates, all to determine the sample size ? In a simulation study of multilevel model, authors chose that combination of sample size...
  10. E

    Determine sample size to get a statistically significant result

    Hello, this question concerns the topic of A/B split-testing. More about it on wiki here. I need to determine what is sample size would I require to get a statistically significant result for my experiment. I can see how an economist at Google is doing it. However, our don't understand the...
  11. N

    Bayesian inference with unequal sampling

    I have a "two-column" data set, with a multi-class categorical variable A, and two-class variable B. It is assumed that each observation is independent. For each category of variable A, I want to make a Bayesian estimate of a binomial parameter for class 1 of variable B, consistent with the...
  12. B

    [Discrete test sample size] Number of samples to test after failures occur

    Hello, I work as an engineer at a large manufacturer and we typically use high stress tests on new products to discover failure modes. Sometimes when we have failures, we attempt to fix the problem and want to re-run the test to see if we were successful. The most obvious question then and...
  13. P

    Deducing Sample Size from Sample Proportion CI

    How do I approach this problem? Suppose we want to estimate a sample proportion to within 0.05 with 95% confidence, how large will the sample have to be? There is no other information about the distributions of the population or the sample. No point in trying to solve for n in the...
  14. M

    Sample size in equivalence trial?

    Hey all, For my thesis I need to calculate the sample size for an equivalence trial with four groups (the score on four equivalent forms in order to prove they are indeed equivalent). The study is done before with only one of the four forms, they found a mean = 19.8, SD = 2.0, tolerance =...
  15. R

    Incidence rate in a cohort with small sample size

    I have a small cohort of people with a specific disease (n=300) and studying the incidence of a related disease (which is kind of rare and normally occur only as a subsequence of this main disease). I have longitudinal data for this cohort over 4 years and I am fine with the study design in...
  16. N

    Arriving at sample size the correct way.

    Dear members, I have a large group of our customers who have transacted with us once. I would like pick up a sample group of customers from this available group mentioned above for an experiment. The experiment I would like to do is I would like to gain insights in their behavior as to...
  17. N

    Picking up a sample size of customers the statistics way?

    Dear members, I have a large group of our customers who have transacted with us once. I would like pick up a sample group of customers from this available group mentioned above for an experiment. The experiment I would like to do is I would like to gain insights in their behavior as to...
  18. D

    order determination sample size for autoregression

    Hi I am new to autoregression. I want to determine the order of an autoregression given a sample of size S1. I plan to use ordinary least squares on the sample S1 to determine the coefficients. My query is whether I can use a smaller sample size S2 to determine the order, and use the...
  19. M

    sample size calcs - why do these produce different results

    What are the interpretations for each of these? data a; input z p q e; cards; 1.96 0.95 0.05 0.05 ; data b; set a; n=(z*z*p*q)/(e*e); run; proc print; run; ****************************; proc power; onesamplefreq test=z method=normal sides =...
  20. S

    Bigger sample size and less good results or smaller sample size but better results

    I hope this is the right place to post this question. I'm doing my thesis based upon the data of my professors research study. I want to look into wether 2 different psychological treatment conditions affect social phobia compared to a control group, how they differ, and wether former...