power calculation

  1. B

    Calculating Power

    Hi Everyone, I am doing a correlation analysis to see which variables impact the quota achievement of a set of sales reps at my company. I am trying to figure out how significant my results are, but am not sure if I am calculating the statistical power the right way. I'm grouping quota...
  2. 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...
  3. D

    Sample Size Calculation/power calcuation for retrospective study

    Hi all, I recently completed a study looking at hospital records over a 5 year period (fixed population of participants based on study period). We looked at 'blood transfusion' as a binary measure (didn't receive a transfusion = 0, did receive a transfusion = 1) between three groups...
  4. A

    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...
  5. 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...
  6. 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...
  7. 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...
  8. M

    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...
  9. 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...
  10. O

    Confusing Power of T Test!

    Hey all, This is my first post to this site. My question is: I am using this (given) regression to find the relationship between gender and wage: Lnwage = Beta0 + Beta1male + Beta2Professional + Beta3Management + Beta4Educ + u My professor wants me to test the power of the test with...
  11. M

    Power analysis in a repeated measures desgin

    Hi We are planning a randomised clinical trial treating patients with either an active drug or placebo in 20 weeks. We measure the dependent variable several times during the study and want to evaluate the efficacy of the drug at week 20 in respect to placebo. The analysis will be within a...
  12. C

    Calculating the size of Type 1 error, Type 2 error and power of the test

    Let X have a binomial distribution with parameter n=5 and P\in [p:p=\frac{1}{4},\frac{1}{2}]. The null hypothesis H_{0}:P=\frac{1}{4} is rejected, and The alternative hypothesis H_a:P=\frac{1}{2} is accepted. If the observed value of X_1, a random sample of size one, is less than or equal...
  13. A

    Deciding on test and help with power, thank you!

    Hi there, I'm a first year PhD student and I am a bit at a loss regarding which test to use, and how to calculate power for a grant proposal. Any help will be much appreciated! I'm running all my participants in two conditions (positive/negative), so a within-subject design My dependent...
  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. T

    Calculating Sample Size for a prospective/longitudinal study

    I am an undergraduate conducting a literature review. I am wanting to discuss sample size among the papers I am critiquing. The papers I am analyzing are studying hearing impaired populations over a given time, to discover whether they are more susceptible to cognitive decline. How do I...
  16. Z

    Power Calculation using Stata

    Hi, I am involved in a clinical study where I need to ascertain that the study has adequate power. The study aims at understanding the effect of a program on patients. We are required to have a control and a treatment sample. I believe I can recruit about 22 individuals for the study in each...