power analysis

  1. K

    Power Calculation

    Hi, I have a power calculation question. I have an initial study that has 6 subjects (all treatment group) and a follow-up study with 60 subjects (randomized into treatment and placebo 1:1). Can I find the probability of any of the 60 subjects experiencing an Adverse event, if >=33% of the...
  2. J

    Pairwise Comparison Study Stats

    Hi, I'm looking to carry out a study which will involve a pairwise choice comparison. I am aiming to identify any patterns of preference by wild individuals (measured by abundance) when presented with four different types of refuge. I will be conducting it in the form of pairwise choice...
  3. S

    power analysis/ sample size

    Dear reader, I would like to conduct a clinical study in which I compare 2 treatments. The goal is to determine which one cures the lesion faster. There are currently no studies comparing these two treatments head to head but there are studies comparing them to placebo. According to the...
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  5. 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...
  6. P

    Power analysis for time series regression

    Hello, I'm trying to determine the sample size I need for a study. In the analysis, I will be including three predictors (score on a questionnaire, time, scorextime interaction) and one outcome variable. I am only using one group of individuals and collecting data at baseline, time 1, time 2...
  7. P

    Power analysis for 3-way interaction with 1 between-, 2 within-subjects factors

    Hi all, I am trying to use G*Power 4 to compute the sample size that I will need to detect a 3-way interaction (2 x 2 x 2) in a mixed-effect ANOVA with 2 repeated-measures factors and 1 between groups factor. Do I just add the two levels of the second repeated-measures factor to the...
  8. E

    Sensitivity analysis said I wouldn't find an effect less than .8 but I did!

    Hello! I ran a sensitivity analysis on G*power and it told me that for my independent samples t test (10 people per group, alpha = .05, power =.8) I wouldn't find an effect size smaller than d = 1.32. I then ran the t test and got a significant result with an d = 1.15 How is this possible?
  9. N

    Post-Hoc Power Analysis (G*Power) for simple linear regression

    Hey everyone! I conducted a simple linear regression with non-significant results. Now I would like to analyze the power of this calculation using G*Power. I chose the option "F-tests - Linear multiple regression, fixedmodel, R(2) deviation from zero and entered 1 as my numer of predictors...
  10. F

    A priori Power Analysis

    Hey Guys, I am a newbie and have a question on power analysis. I would like to measure the effect of an intervention on various measures and have several control variables. I believe it is the best to use a multiple linear regression model with a dummy variable for the treatment. Therefore, I...
  11. R

    power calculation for two groups (parallel)

    Hi I have got 400 and 600 samples in control and test groups respectively. And in each of these two groups, i have an effect variable that occurs at the rate of 30%. this is a retrospective data analysis. I want to investigate whether the effect variable impairs the patient outcome (response...
  12. A

    help needed with Fishers Exact Test (power calculation)

    Hello everyone. Hope someone can help me. I am running a Fisher exact 4 X 2 table analysis in SPSS. I have been informed its the correct test to use for the data. The problem is I have to conduct a power analysis to determine how many in both groups i need to be able to detect significance...
  13. R

    Power Analysis

    Hi there, I am currently writing a statistics report which has to cover 2 questions: Firstly, what the correlation is between two different test scores of 30 participants. Secondly, what the power of the study is. I am really struggling to grasp what the pro's of doing a post-hoc power...
  14. 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...
  15. 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...
  16. 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...
  17. E

    McNemar's test post-hoc power analysis problem when odds ratio=0

    I need to do post-hoc power analysis for a McNemar's test (using G*power), and am having trouble getting results. One of the discordant pairs is 0, therefore the odds ratio is zero, and it seems that power cannot be calculated using an odds ratio of 0. Is there any way around this...
  18. J

    Determining sample size in a factorial repeated measures ANOVA using GPower

    Hi all Can anybody tell me which F-test option in G power is appropriate to find out the sample size for a 2x2x2 repeated measures ANOVA? The three within subjects factors are A, B & C. I am interested in finding out how many subjects I will require to find a main effect of A...
  19. C

    Power Analysis and Sample Size determination help!

    Hi all! I am new here so I hope my post is appropriate! I have searched the web and this forum and haven't been able to figure out how exactly I need to perform a power analysis for sample size determination (although I admit I didn't scroll through ALL of the results to my search on this...
  20. 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...