sample size

  1. 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 =...
  2. 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...
  3. J

    Futility analysis sample size

    Hello, I have been asked to determine the sample size needed to demonstrate futility in a small study. I suggested going the "traditional route" and conducting an interim analysis at a pre-specified timepoint or sample size to determine whether or not to continue (likely via conditional power)...
  4. W

    Sample size during error propagation calculation

    Hi, I have several questions regarding the calculation of error propagation. Assuming I have a group of 'A' data with mean =0.852361, sd=0.388232 and sample size=34. And I have another group of 'B' data with mean = 0.798698, sd=0.396084 and sample size=40. Now I want to calculate the...
  5. L

    Central limit theorem effect of number of samples vs sample size

    Hey guys, For an assignment I've been asked to investigate the CLT when sampling from different distributions using different sample sizes. Do to this in R, I've created histograms of the binomial, poisson, and uniform distribution each with 10, 100, 1000 samples of sample sizes of 10, 20...
  6. K

    sample size calculation for paired proportions when one discordant pair is 0

    Hello! I am trying to calculate sample size for a study using paired data. My groups are such that one discordant pair will always be 0. I planned to use McNemar to test for a difference between the groups, however, I am not sure this is valid since one discordant pair will always be zero...
  7. I

    How to determine number of data points and period of data to determine confidence?

    Dear Statisticians I have done some experiments, with continuously data acquisition, on shrinkage measurements over time. My data shows exponential regression curves. Based on the data I want to estimate how many data points and at what time the data should be gathered, to obtain a certainty...
  8. B

    Sample Size for Prevalence Study

    Hi All, I was hoping to get some advice on how to use the following formula to estimate sample size for a prevalence study (paper with exact formula can be found here: http://www.kck.usm.my/ppsg/aos/Vol_1/09_14_Ayub.pdf): n = Z2P(1 – P) d2 Where: n = sample size Z...
  9. G

    Minimum 5 defectives rule of thumb

    I have taught six sigma black belt classes using consultant sourced training materials which included the rule of thumb that when estimating the rate of occurrence of discreet events, like the proportion of defective units produced by a manufacturing process, a sample size large enough to...
  10. P

    Sample size determination (margin of error)

    Hi all, I notice my organization does not follow to NIST standards and I seek for help from the community: All the while, my company has been using the following; and I am often confused on the validity: The binomial equation used to predict the probability of a specific number of r...
  11. L

    Partial spearman correlations and normality

    hello I am trying to conduct partial spearman rho correlations with syntax. However, I have different controls for my different variables. For example, with one variable I have 3 controls and another variable I have 5 controls. I am using the syntax from here...
  12. A

    What hypothesis test?

    I have a population of Z items, where X must pass and Y must fail. The thing is that the X that pass is not just a count (i.e. if 2 must pass, it has to be items A and B. It can't be C and D.) How do I figure out the sample size/what test should I use to test this? Also, how would I test it...
  13. M

    Groups in a variable are largely unequal in size

    Hi, I want to run an analysis on a data set. However, the primary predictor variable (5 point scale) varies greatly in size of each group. I plan to create a dichotomous variable from these 5 category. the 0 value would include 75.4% of cases (n=1728), while the 1 value would only include...
  14. M

    ANOVA test Samples

    When running a single factor ANOVA test, do the number of subjects, (sample sizes) have to be equal? Can one column have more data than the other twos?
  15. L

    sample size for likert scale quastionnare

    Hi I have a quastionnare with 40, 5-point likert scale quastion. My population size is 500,000. How I could find sample size? I think demorgan table is for binary data and not for likert scale. I appreciate your answer
  16. D

    Minimun sample for a Mann-Whitney U test

    Hello! :wave: What is the minimun sample per group for a Mann-Whitney U test? I appreciate if you give also a reference about it Thanks!
  17. M

    Which test? - Significance of Sample Size

    Hi all, (First-time poster) I'm working with tagging data for 35 tracked fish. Each fish was tracked of 3 seasons, with detections (3873 overall) corresponding to a fish entering the detection area of one of the many placed monitors within the study area. I would like to perform a stats...
  18. L

    Mediation, Bootstrapping and Sample Size

    I'm new to statistics overall, and even newer to mediation but I'm attempting to analyze data using Process for SPSS. Before anything else, do I need a specific minimum sample size and how do I determine this? Does bootstrapping take care of this, and then, how many bootstrapping samples do I...
  19. R

    Determining ideal sample size, testing normality in SPSS, bonferroni adjustment

    Hello all, I am new to the forum. I had a bit of training in statistics and research, particularly statistics in psychology, but I have some basic questions that are holding me back. I would appreciate the help. 1. How can I determine the ideal sample size for a study (upper and lower...
  20. I

    Sample size for superiority trial

    Hey statistigeniuses, I would greatly appreciate some advice regarding a trial I am designing. I want to determine the most comfortable among 4 different materials. Each of these materials are applied to a person's skin at the same time and they are given a questionnaire to evaluate its...