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Forum: Biostatistics

Epidemiology and biostatistics, public health research. GLM, logistic regression, survival analysis, clinical trials.

  1. 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...

    Started by statsSeeker‎, 04-29-2016 01:47 PM
    power, precision, sample size calculation, sample size determination
    • Replies: 0
    • Views: 66
    04-29-2016, 01:47 PM Go to last post
  2. Diagnostic accuracy of two methods tested on longitudinal data/repeated measurements

    To compare two imaging rating methods in detecting growth (ordinal variable + , = , - ) we compared serial MRI's with both methods. We have for...

    Started by SophieBel‎, 02-09-2016 12:24 PM
    • Replies: 2
    • Views: 326
    04-26-2016, 06:06 PM Go to last post
  3. URGENT: What are the statistical limits and biases in this scientific article?

    I need to deliver this exercise in the next 10 hours. QUESTION: What are the statistical limits and biases in this scientific article, which...

    Started by pericles‎, 04-26-2016 01:21 PM
    articles, bias, inference, limits, publication
    • Replies: 0
    • Views: 97
    04-26-2016, 01:21 PM Go to last post
  4. Estimating discordant pairs for McNemar's test sample size

    Dear Friends, This is my first time posting ;) I want to use McNemar's test to determine if diagnostic test A or B has better sensitivity and...

    Started by Aquaman29‎, 04-24-2016 05:57 PM
    • Replies: 0
    • Views: 131
    04-24-2016, 05:57 PM Go to last post
  5. Problems in Cox proportional hazards model, Survival analysis.

    Hello everyone, I got trouble with some problems as following Suppose a Cox proportional hazards model was fit with 2 covariates, smoking status...

    Started by Leon Yo‎, 04-24-2016 12:39 PM
    • Replies: 0
    • Views: 84
    04-24-2016, 12:39 PM Go to last post
  6. ANOVA RCB design; multiple items in groups

    Good day! I have a study that seems to fit the criteria for an ANOVA using a randomized complete block design. The research is on the effect of...

    Started by Johann Kotze‎, 04-24-2016 06:50 AM
    anova, rcb
    • Replies: 0
    • Views: 75
    04-24-2016, 06:50 AM Go to last post
  7. Systematic component variation

    The appendix of the paper of contains a derivation of the systematic component variation SCV. I understand the derivation with exception of the...

    Started by giordano‎, 04-15-2016 02:31 AM
    estimation, variance, variance components
    • Replies: 0
    • Views: 290
    04-15-2016, 02:31 AM Go to last post
  8. Exclamation Inoculated chickens-bacterial load. Non Linear Mixed Model with repeated measures?

    :wave: Help! I have some data I am trying to analyze but was hoping to get some stats help with it. I'm not sure what the best way to analyze it is....

    Started by vet_11‎, 04-13-2016 03:45 AM
    bacterial load; k-wallis, mixed effects model
    • Replies: 0
    • Views: 170
    04-13-2016, 03:45 AM Go to last post
  9. Help with SAS, MANOVA, and Habitat Selection

    Hello everyone, I guess my long story short is does anyone have any experience using SAS to run a MANOVA to determine habitat selection. I have...

    Started by Esoxdiver‎, 04-08-2016 07:19 PM
    • Replies: 0
    • Views: 239
    04-08-2016, 07:19 PM Go to last post
  10. Prognostic study in Imminent Bain Death (IBD)

    Dear all, I am new in this forum. I have an ongoing research and I am dealing with the statistic. In our study we are trying to compare 2...

    Started by pivadoc‎, 04-06-2016 02:56 PM
    • Replies: 0
    • Views: 226
    04-06-2016, 02:56 PM Go to last post
  11. Question regarding p-value interpretation in Group Sequential Designs

    Hello everyone. I have a general question that I would appreciate any input on: Suppose we design a typical group sequential design and to stop...

    Started by trekvana‎, 03-29-2016 03:36 PM
    • Replies: 0
    • Views: 315
    03-29-2016, 03:36 PM Go to last post
  12. Paired analysis of Proportions with Gold Standard Retest

    Greetings :) I'm working on developing a diagnostic test. I have a small clinical dataset that was evaluated with the diagnostic test and a...

    Started by Midgardian‎, 03-29-2016 12:58 PM
    • Replies: 0
    • Views: 139
    03-29-2016, 12:58 PM Go to last post
  13. Sample size calculation in a 3 group parallel clinical trial

    Hello everyone. I'm having trouble with biostatistics in general but particularly with finding out how to calculate what sample size i need in...

    Started by TNK78‎, 03-27-2016 02:58 PM
    • Replies: 8
    • Views: 439
    03-28-2016, 03:21 PM Go to last post
  14. Comparing groups - which test should I use - one-way or two-way ANOVA

    Here is the experiment sum-up: we transplanted limb from one rat to another (n=5 per group), the goal was to find out which treatment was the best in...

    Started by Nataliya‎, 03-28-2016 12:39 PM
    • Replies: 0
    • Views: 129
    03-28-2016, 12:39 PM Go to last post
  15. Predictive value of X for a change in Y?

    Hi everyone, R question: 10 participants underwent a weight loss programme, like so: ...

    Started by RodeLoper‎, 03-24-2016 01:39 PM
    intercept, random effects model, slope
    • Replies: 1
    • Views: 243
    03-25-2016, 02:47 AM Go to last post
  16. Statistical test of difference among values from multiple timepoints

    Hello, I have a question on selecting a statistical test. I am trying to assess changing abundance of microbes in oral cavity along time. My...

    Started by 3toedsloth‎, 03-23-2016 05:25 PM
    • Replies: 0
    • Views: 175
    03-23-2016, 05:25 PM Go to last post
  17. Comparing new and old medical equipment

    ***I'm not sure why this posted twice (and I don't know how to delete this one), but please see the other post with the image attached. Thank...

    Started by DataMom‎, 03-20-2016 05:41 AM
    • Replies: 3
    • Views: 341
    03-20-2016, 11:56 AM Go to last post
  18. Survey regression modeling rates

    I have a nationally representative data set of ~30,000 emergency department visits in a year; using the provided weights, these represent ~200...

    Started by subharimc‎, 03-18-2016 11:39 AM
    • Replies: 0
    • Views: 187
    03-18-2016, 11:39 AM Go to last post
  19. Research methodology question

    We are implementing a new community healthcare program at work in order to reduce hospital attendances and admissions. The program began in June...

    Started by scotchpie‎, 03-17-2016 09:56 AM
    • Replies: 2
    • Views: 196
    03-17-2016, 11:30 AM Go to last post
  20. Power analysis and Kaplan meier

    Hello! I need your help to compute a power analysis for survival analysis (Kaplan meier) without historical data. In my lab we are preparing a...

    Started by Fischer‎, 03-17-2016 09:00 AM
    • Replies: 0
    • Views: 136
    03-17-2016, 09:00 AM Go to last post
  21. best modeling approach?

    I have a data set with about 5000 pts and trying to create a risk prediction model to predict binary outcome that does not have competing risks...

    Started by viostorm‎, 03-15-2016 05:31 PM
    • Replies: 5
    • Views: 410
    03-16-2016, 07:53 PM Go to last post
  22. Is my study a case control or a cohort study?

    Hi everyone. I'm a student with very little experience or background in biostatistics. My mind is in a bit of a bind and I can't seem to be able to...

    Started by sadrith‎, 03-16-2016 01:01 PM
    • Replies: 1
    • Views: 180
    03-16-2016, 02:22 PM Go to last post
  23. Repeated measure ANOVA

    Hello guys, Haven’t done stats for 15 years, and been struggling for weeks now on an ANOVA, lost in a rural area in Haiti with limited access to...

    Started by Libellule‎, 03-15-2016 04:46 PM
    • Replies: 2
    • Views: 161
    03-16-2016, 09:09 AM Go to last post
  24. Computing effect size with adverse event counts?

    Hello! I'm working on a meta-analysis, and I have a special problem regarding effect size. Can anyone lend me some insight? I have a treatment...

    Started by wag‎, 03-14-2016 02:26 PM
    • Replies: 0
    • Views: 176
    03-14-2016, 02:26 PM Go to last post
  25. estimate of measures

    Hello everyone, I am a statistics student, I'm studying for a project in my University. I have to analyze the data, I have available the measures in...

    Started by andrew_fg‎, 03-12-2016 04:42 AM
    biostats, estimate
    • Replies: 1
    • Views: 219
    03-12-2016, 06:00 AM Go to last post
  26. Wink Justification for t-tests instead of 2-way ANOVA (no interaction)

    HI there, I need help with justification for why I should use a t-test instead of a two-way ANOVA. My two-way ANOVA gave me a main effect of Diet...

    Started by dulcedumbre‎, 03-11-2016 10:05 AM
    justification, no interaction, t-test, two-way anova
    • Replies: 3
    • Views: 222
    03-11-2016, 12:43 PM Go to last post
  27. An associate for publishing studies?

    Hello friends. I am a Ph.D. student in medicine. Untill now I have published four scientific papers (two of them, meta-analyses). I have also...

    Started by bioresearcher‎, 03-11-2016 09:07 AM
    • Replies: 0
    • Views: 118
    03-11-2016, 09:07 AM Go to last post
  28. sample size calculations

    So, i'm in the process of setting up a trial comparing two different methods of observation and I need to calculate the sample size. I plan on...

    Started by sigge weisdorf‎, 03-11-2016 07:48 AM
    • Replies: 0
    • Views: 97
    03-11-2016, 07:48 AM Go to last post
  29. Correcting for a confounding factor in a retrospective laser eye surgery study

    Hello, I would really appreciate some help on study design. I will present my ideas and if the forum could critique/advise I would be very...

    Started by eyedocdan‎, 03-04-2016 01:37 PM
    • Replies: 5
    • Views: 560
    03-06-2016, 09:49 PM Go to last post
  30. statistical test for a cancer vs normal comparison from the same patient

    Hello, I have a question concerning which statistical test is best for analyzing my data. I measured the activity of an enzyme in primary cells...

    Started by vanida‎, 02-27-2016 04:33 PM
    • Replies: 2
    • Views: 414
    03-05-2016, 04:33 PM Go to last post
  31. Interpreting Kruskal-Wallis test

    My question arises from a paper I read. Two groups are compared using the non-parametric Kruskal-Wallis test. Neither group has data that is normally...

    Started by JRA‎, 03-01-2016 01:16 PM
    • Replies: 7
    • Views: 411
    03-04-2016, 01:47 AM Go to last post
  32. Small sample: Descriptive or analytical? Adjust or not?

    Hi, I need help with choosing which tests to use, as well as the goal of the testing. I am sure some of my questions are answered already on this...

    Started by teapot‎, 03-01-2016 11:11 PM
    • Replies: 1
    • Views: 257
    03-02-2016, 05:41 AM Go to last post
  33. Question regarding sample in EBP project

    Hi, I was hoping someone could provide me with some insight for an evidence based practice project I am working on. I'm currently appraising...

    Started by abreckenridge‎, 03-01-2016 12:46 PM
    • Replies: 1
    • Views: 147
    03-01-2016, 01:12 PM Go to last post
  34. 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...

    Started by trancine‎, 03-01-2016 07:43 AM
    clinical trial, confidence intervals, effect size, power analysis, sample size
    • Replies: 2
    • Views: 209
    03-01-2016, 10:39 AM Go to last post
  35. By wastewater treatment microbial technology

    :làn sóng: Wastewater from residential areas, urban collection tank was brought before collection tank sewage systems of automatic duplex to separate...

    Started by moitruongtnt‎, 02-27-2016 10:58 AM
    wastewater treatment
    • Replies: 0
    • Views: 161
    02-27-2016, 10:58 AM Go to last post
  36. Adjusting for clustered observations

    Hello, I have collected mortality data and several covariates (data on treatment and vital parameters) from patients in two different hospitals....

    Started by Patrick‎, 02-22-2016 02:52 AM
    fixed effect, gee, logistic regression, random effect
    • Replies: 5
    • Views: 335
    02-25-2016, 11:17 AM Go to last post
  37. Smile Selecting an appropriate spatial scale in landscape ecology!?

    Hello, I am currently studying the effect of organic farming on honeybee colonies. I have calculated the percentage of organic land in several...

    Started by master student‎, 02-25-2016 08:27 AM
    data mining, landscape ecology, spatial scale
    • Replies: 0
    • Views: 152
    02-25-2016, 08:27 AM Go to last post
  38. Am I introducing a selection bias in my prognostic biomarker study ?

    Hi all, I'd be glad to get the advice from someone who's better than me at biostatistics, especially regarding selection biases in survival...

    Started by Debby 02‎, 02-23-2016 04:14 PM
    • Replies: 5
    • Views: 300
    02-24-2016, 08:12 AM Go to last post
  39. Cox regression with 6 variables in 30-something patients sample, is it legitimate?

    Hi, I'm doing some research and I have a sample of 33 patients. I'm testing an association of one new parameter (let's call it X) on survival and...

    Started by Markica85‎, 02-21-2016 05:25 PM
    • Replies: 0
    • Views: 208
    02-21-2016, 05:25 PM Go to last post
  40. Kruskal-Wallis and post-hoc tests

    Hi, Can I do post-hoc tests, such as Scheffé's test, while I'm performing a Kruskal-Wallis test? Thanks.

    Started by Biologist‎, 02-19-2016 03:20 PM
    • Replies: 2
    • Views: 275
    02-21-2016, 06:33 AM Go to last post
  41. How meaningful is to pool data from different surveys on the same target population?

    HI everybody, this is a very theoretical question for me but I would like to find an answer as I might want to use this in the (near) future. In...

    Started by Ralph84‎, 02-15-2016 12:50 PM
    pooled estimates, pooling data, survey weights
    • Replies: 3
    • Views: 326
    02-16-2016, 04:06 AM Go to last post
  42. Why regression models use log or exponential value?

    I am not very familiar with statistic. Any statistician can help me to clarify what the difference are between exponential value and log value. I...

    Started by mee mee‎, 02-15-2016 07:38 PM
    biostatistician, exponential, log-linear
    • Replies: 1
    • Views: 193
    02-15-2016, 08:11 PM Go to last post
  43. HLM Unit Specific vs. Population Average Model

    I am using HLM to do a 2 level longitudinal analysis of change in firearm background check denial rate. The denial rate per 100,000 is the outcome....

    Started by muelledg‎, 02-12-2016 01:11 PM
    • Replies: 2
    • Views: 308
    02-14-2016, 10:47 PM Go to last post
  44. Post Median Fold Change and Interquartile Range. 2 non-normal non-paired groups.

    I have a query concerning data presentation using biological data. I would like to present the median fold change between a control and test...

    Started by phdmedsci‎, 02-12-2016 12:13 PM
    interquartile range, median fold change, medical science, non-normal distribution
    • Replies: 0
    • Views: 166
    02-12-2016, 12:13 PM Go to last post
  45. Prospective study. What test would be appropriate?

    Hey there! I am practicing on these data I have and I want to apply a statistical test. I want to compare 2 treatments: evolution and incidence...

    Started by Flaviviridae‎, 02-10-2016 11:14 AM
    • Replies: 6
    • Views: 344
    02-11-2016, 02:31 PM Go to last post
  46. Ploting continuous caracter on a phylogenetic tree

    Hi, I study comparative biology and have been trying to estimate ancestral character states for continuous characters using the package phytools. ...

    Started by jessicafratani‎, 02-10-2016 12:42 PM
    • Replies: 4
    • Views: 294
    02-10-2016, 04:59 PM Go to last post
  47. Rows or columns?

    In a clinical statistics workshop we were given this question? Can anyone help me, I've been tearing my hair about it: A case control study of...

    Started by gillis‎, 02-08-2016 02:42 PM
    • Replies: 1
    • Views: 264
    02-09-2016, 03:22 AM Go to last post
  48. Please help me! I am stuck choosing which model to use! :(

    Hello! I have been reading so much about stats that I am a bit confused now.. I have samples from an experiment in which I have counted cells. So I...

    Started by Cats‎, 02-08-2016 07:56 PM
    multilevel modeling, nested
    • Replies: 1
    • Views: 249
    02-09-2016, 12:23 AM Go to last post
  49. Which test should I use?

    Hello There: I am wondering which test to use for this question: Does the involvement in child welfare in an participants’ life increase the...

    Started by gbgb‎, 01-28-2016 09:09 PM
    • Replies: 2
    • Views: 343
    02-07-2016, 12:35 PM Go to last post
  50. Help

    Ok, so here is my problem, I have a patient list of 300 patients each with unique identifiers like age, sex, race. Each patient is numbered 0001,...

    Started by iamrico00‎, 02-04-2016 01:06 PM
    • Replies: 0
    • Views: 283
    02-04-2016, 01:06 PM Go to last post
  51. Pre-post test for same group (no control), controlling for confounding

    Which Test to use & How to use in SPSS? MY situation: In a single group, pre post intervention scenario, i wan to test whether the change in...

    Started by HBS‎, 02-03-2016 12:40 PM
    • Replies: 4
    • Views: 401
    02-04-2016, 04:00 AM Go to last post
  52. Averaging and comparing mean values across studies

    I am having a statistical problem that falls into two parts: (!) I have several literature reports on studies that have investigated the effect of...

    Started by AVoelp‎, 02-03-2016 08:04 AM
    • Replies: 0
    • Views: 211
    02-03-2016, 08:04 AM Go to last post
  53. Back transformation for log-transformed variables in Cox regression

    I have to perform a meta-analysis. My problem is that in a number of studies, the HRs for the explanatory variable are reported for the log...

    Started by Dimitrie‎, 02-02-2016 03:20 AM
    • Replies: 0
    • Views: 220
    02-02-2016, 03:20 AM Go to last post
  54. Question- student paired sample t test, wilcoxon signed rank test

    Hi, I have samples that are not expected to be normally distributed, I treat them with and without a compound and perform statistical analysis. I...

    Started by AggieTheBird‎, 01-26-2016 02:28 AM
    • Replies: 3
    • Views: 407
    01-31-2016, 01:58 AM Go to last post
  55. Measuring disease severity of PAIRS of eyes between treated and untreated groups

    Dear forum. Would someone please beable to provide me some advice on which statistical analysis to apply to an aspect of my PhD data... I am...

    Started by CrossRoe‎, 01-29-2016 08:06 AM
    eyes, paired samples
    • Replies: 3
    • Views: 358
    01-29-2016, 09:01 AM Go to last post
  56. Post N of 1 study looking at complex phenotypes and SNPs

    Hi All, I have a complicated question and can't find a resource that answers it comprehensively. I'm designing a study looking for linkage between a...

    Started by keri‎, 01-27-2016 04:49 PM
    biostatistics, complex disease, complex variables, linear regression, snp
    • Replies: 0
    • Views: 224
    01-27-2016, 04:49 PM Go to last post
  57. Equivalence limit in Bioequivalence studies

    Hi All, Need this input from you..in bioequivalence studies, can we use the equivalence limit of (-0.2) instead of (+0.2) since the range is...

    Started by charan.kumar.kj@gmail.com‎, 01-25-2016 01:52 AM
    • Replies: 1
    • Views: 259
    01-25-2016, 03:18 AM Go to last post
  58. Smile Intention to treat analysis and estimating loss to follow up

    Hi guys, Doing my MSc in Clinical Trials and after looking at a research paper I am stumped about something... The authors have stated that...

    Started by clinicaltrialsnewb‎, 01-23-2016 10:34 PM
    • Replies: 2
    • Views: 312
    01-24-2016, 10:55 AM Go to last post
  59. question about survival analysis and late entry data

    I have a large ongoing national longitudinal survey data. The original cohort contains people between age 51-61 in 1992. Since the beginning of the...

    Started by sunny3333‎, 01-19-2016 01:05 PM
    • Replies: 3
    • Views: 384
    01-20-2016, 07:03 AM Go to last post
  60. Calculating control group in chi square test

    I'm trying to compare the prevalence rate of autism in offspring of mothers with and without gestational diabetes. I gathered data from 1000 women, 8...

    Started by Michalus‎, 01-15-2016 08:11 PM
    • Replies: 2
    • Views: 552
    01-16-2016, 07:48 AM Go to last post

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