# sample size

1. ### Need help with power analysis GPower Novice

Hello everyone. I am doing a power test for Fishers Exact Test on GPower, and dont know how to determine the proportions p1 and p2. I have 2 categories that im looking at if there is a difference between one and other across 4 rows. How would i calculate the P1 and P2 for this. Basically i...

I'm asking a group of young people who have experienced loss to complete the Posttraumatic Growth Inventory and then a sheet about different factors identified in previous research (age, gender, support network, religious beliefs, etc). I then want to see if there are any correlations between...
3. ### 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...
4. ### 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...
5. ### Relationship between effect size, sample size and p-value?

Is there a simple formula that links effect size, sample size and p-value? Specifically, how does the p-value depend on effect size and sample size? Are there any other critical factors involved in this relationship? I'm basically looking to understand how these factors are linked...
6. ### Power and sample size calculation for neuroscience

Dear TalkStats, I have searched the forum but cannot find the answer I am looking for, if you could help that would be great! I am recording cells and their action potential frequency in two conditions (group 1 and group 2). (So it is a repeated measures.) How do I calculate the required...

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...
8. ### 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...
9. ### 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...
10. ### 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...
11. ### 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...
12. ### 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...
13. ### 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...
14. ### 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...
15. ### 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...
16. ### 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...
17. ### 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...
18. ### [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...
19. ### 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...
20. ### 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 =...