sample size determination

  1. L

    Standard error calculation for more than one sample size

    Hi all I am conducting a meta analysis of pearsons r correlations. Whenever a study has presented more than one correlation I have averaged them into one correlation by converting them into fishers z scores. I now have the problem that I need to calculate a standard error and variance of the...
  2. 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/...
  3. 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...
  4. 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...
  5. 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...
  6. A

    Appropriate sample size for unusual "populations"

    There seems to be a lot of literature about determining sample size based on population, margin of error and confidence level. This seems difficult to apply to surveys where the "population" consists of large institutions. For example, say it's a survey on investment allocation by public...
  7. 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...
  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. 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...
  10. P

    How to select the training dataset

    I have a dataset which contains dependent variance Y and several independent variances X1, ... , X10. Y has 5 possible values: A, B, C, D, E, a proportion of each value is: A: 80%, B:10%, C:5%, D:3%, E:2%. I want to build a model to predict the value of Y, I decide to pick up 70% of the...
  11. H

    Min sample size for Wilcoxon Rank Sum test

    Hi, I have data measurements (eg, running cost) that keep coming in to the system continuously. There are two groups (say X and Y) that I want to compare. I want to see which one is systematically larger (H1: X > Y?). However, I have a couple of issue with my data: i) I can't assume normality...
  12. M

    Group Size for Binary Logistic Regression

    I am trying to determine the odds ratio for the effect of C on A. However, my is a sample of n = 45 with 4 = yes and 41 = no. Is this small group size a major issue, and how do test for power in this case? THANKS!
  13. B

    Estimating sample size for reliability study

    Hello, I'm having problems calculating the required sample size for my PhD study. I have designed my first study, which is comparing moral reasoning abilities in people with a brain injury to a healthy comparison group. I have used previous similar research and G Power to estimate the...
  14. L

    Minimum sample size for moderation analysis

    Hi everyone, And thanks for the great job you are doing here. I have a question regarding statistical power and regression. How can I calculate the minimum sample size based on the number of moderators I have in multiple regression? Is there an online tool for this? If for example I have 5...
  15. L

    Please help - Sample size calculation

    I am designing a study in which a new drug x is given to patients on drug y and then drug y is withdrawn. If the required success rate is 80%: How should I calculate a sample size with a power of 90%? Thanks for your help.
  16. P

    Sample size - chi-squared vs. normal

    Hi, I apologise if this is the wrong thread. I need to calculate sample sizes, but I'm curious as to why the commonly used Krejcie-Morgan tables use a chi-squared formula rather than a student-t or a normal distribution. I see quite a few other papers that use the latter distributions...
  17. Y

    help with study sample size and statistical analysis

    Hi, I'm in the preparation stages of an RCT looking to assert the effectiveness of psychological therapies for a health condition. The design will be a 3 parallel arm RCT, comparing high intensity CBT, low intensity CBT and usual care. We are thinking of collecting baseline measures (2...
  18. B

    Unblinding Concern: Projecting Last Event in > 2 Arm Study....

    In a two arm time to event study one can use various blinded projection methods using the aggregate event rate to estimate when the last event may occur. Now, lets say one has a three arm study where two different doses of an experimental drug are compared to a control. In addition each...
  19. R

    sample size determination using a population range

    Hi. I have a problem about sample size determination. The population of interest is somewhat vague. What I know about the population is only the population range R, i.e, R = max value - min value in the population. I don't know the population distribution, also. Is it possible to...