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Forum: Biostatistics

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

  1. External Validation of Cox Model

    I have two data set (training and validation) for building and validating a Cox model. With the training data set I fitted a cox model using...

    Started by Jyde‎, 06-28-2016 05:17 AM
    cox proportional hazard, sas clinical, survival analysis, validation
    • Replies: 8
    • Views: 145
    Yesterday, 04:18 AM Go to last post
  2. Help interpreting an interaction in Binary Logistic Regression

    Firstly, thank you for taking the time to read my problem that I am having. The goal: interpret the direction of the interaction term. ...

    Started by 2+2=5‎, 06-25-2016 09:50 AM
    interaction effect, logisitic regression, logistic interaction
    • Replies: 3
    • Views: 189
    06-25-2016, 04:05 PM Go to last post
  3. Calculating standard deviation from mean and P value

    I am doing a systematic review and one of the papers I am including has reported the data only as mean, sample size and P value. I need the mean and...

    Started by CMP‎, 06-22-2016 03:35 PM
    • Replies: 10
    • Views: 324
    06-24-2016, 10:10 AM Go to last post
  4. Permutation correlation with one non-normal variable

    Hi, I am trying to assess the relationship between a relatively normally distributed variable (brain volume) and a strongly right-skewed...

    Started by nielsl‎, 06-23-2016 03:06 AM
    correlation, pearson, permutation
    • Replies: 1
    • Views: 118
    06-24-2016, 02:45 AM Go to last post
  5. 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: 1
    • Views: 310
    06-22-2016, 05:34 PM Go to last post
  6. Triple crossover study and multivariate model with paired data

    Hi, I would like to analyze data from a triple crossover study. Same population received same drug (or placebo) three times a day with...

    Started by Markica85‎, 05-28-2016 03:51 AM
    • Replies: 1
    • Views: 260
    06-21-2016, 06:50 AM Go to last post
  7. Question Statistical Approach for data (uneven intervals)

    Hello, What statistical approach would you recommend for a data of the following pattern. In a 12-hour window, each row/ID is an independent...

    Started by rvr‎, 06-20-2016 12:23 PM
    frequency distribution, model selection, statistical approach, time interval, uneven tests taken
    • Replies: 0
    • Views: 115
    06-20-2016, 12:23 PM Go to last post
  8. Test for ordinal DV in mixed design

    What's the corresponding test to Two way Mixed ANOVA when the DV is ordinal? I have two treatment groups, 14 time points and the DV is an ordinal...

    Started by Logician‎, 06-14-2016 06:55 PM
    • Replies: 0
    • Views: 465
    06-14-2016, 06:55 PM Go to last post
  9. How to construct a scatter graph with percentiles lines

    Good day, How to construct a scatter graph with percentiles lines, like the one in the image below, with any program ?

    Started by tonia bird‎, 06-04-2016 01:35 PM
    • Replies: 3
    • Views: 440
    06-11-2016, 06:13 PM Go to last post
  10. Repeatability and Logistic Regression?

    Hi all, my stats knowledge is quite basic so I would appreciate any help you can provide! I am working on a study looking at inter-grader and...

    Started by StatsN00bie‎, 06-10-2016 01:04 PM
    • Replies: 2
    • Views: 221
    06-10-2016, 02:02 PM Go to last post
  11. Is this study a case-control or retrospective cohort?

    "Recently we retrospectively examined the spine on pyelograms of 34 children with Wilms tumour. The findings were compared with those obtained in 148...

    Started by klionj‎, 06-02-2016 11:44 PM
    • Replies: 0
    • Views: 194
    06-02-2016, 11:44 PM Go to last post
  12. Significance of a Dichotomous Variable Over a Continuous Variable

    Hi all! I ran an analysis using the 2005 healthy eating index (HEI) score as the dependent variable and am a bit confused by my results. The HEI...

    Started by tnrose87‎, 05-31-2016 07:12 PM
    • Replies: 1
    • Views: 194
    06-01-2016, 06:24 AM Go to last post
  13. Chi Square for Molecular Screening Comparison

    Hi, I'm trying to run a chi square test to compare two different screening methods for a pathogen. I'm testing this by diluting a known positive...

    Started by OMai‎, 05-31-2016 03:59 PM
    • Replies: 0
    • Views: 104
    05-31-2016, 03:59 PM Go to last post
  14. Best Statistical test for data

    Hi All, Just wondering if someone could help with an issue with my data. I am wanting to analyse the relationship between continuous variable...

    Started by HRS‎, 05-25-2016 03:48 AM
    • Replies: 3
    • Views: 285
    05-26-2016, 06:49 AM Go to last post
  15. ANCOVA assmptions not met.

    Hi, What is the non parametric alternative for parametric ANCOVA if we find that some ANCOVA assumptions are not met? How it can be done in SAS?

    Started by shruti verma‎, 05-25-2016 03:46 AM
    analysis, analysis of covariance, ancova, assumptions
    • Replies: 1
    • Views: 115
    05-25-2016, 04:03 AM Go to last post
  16. Score methods

    Hello everyone, I would like your opinion. my data is score (before and after therapy) on radiographs made with x-ray instrument and score based on...

    Started by andrew_fg‎, 05-23-2016 01:47 PM
    • Replies: 2
    • Views: 173
    05-24-2016, 01:55 PM Go to last post
  17. Please help me selecting a test for my study

    Hi, I was wondering if you guys can provide some ideas on best test for my samples size, since I am not very stat savvy. My project consist of...

    Started by kite6k‎, 05-18-2016 12:07 PM
    • Replies: 4
    • Views: 222
    05-24-2016, 09:03 AM Go to last post
  18. Frequency analysis

    Hello. I have a problem with my analysis. I got 2 groups which take drug (Group 1 (50 people) takes real medicine and Group 2 (40 people) takes...

    Started by Makina‎, 05-20-2016 04:50 AM
    • Replies: 7
    • Views: 312
    05-23-2016, 08:12 AM Go to last post
  19. Paired or Unpaired T-test?

    If I have traps set to capture a certain animal at night vs. during the day, would I use a paired or unpaired T-test? I'd be comparing the mean...

    Started by OMai‎, 05-22-2016 10:59 AM
    paired, t-test, unpaired
    • Replies: 1
    • Views: 148
    05-22-2016, 12:47 PM Go to last post
  20. Non parametric multivariate analysis. maybe :(

    Hello to everyone, i need some help with my statistical analysis. I have two different pharmacokinetic parameters. They result from two different...

    Started by bluina‎, 05-11-2016 03:38 AM
    biostatistics, multivariate analysis, non parametric
    • Replies: 4
    • Views: 302
    05-20-2016, 04:07 AM Go to last post
  21. Which statistical test shoud I use?

    I have concentrations of one metal in two organs of a snail – kidney and foot (n=10). What statistical test should I use to check if the difference...

    Started by Miii‎, 05-19-2016 06:36 AM
    • Replies: 7
    • Views: 234
    05-19-2016, 02:27 PM Go to last post
  22. LD50 and ED50 calculation with Probit and other methods

    hello All i'm not have good experiences in bio-statistic and want to know how can i calculate LD50 for Bacteria and ED50 for Bacterial Vaccine...

    Started by mazan2010‎, 05-18-2016 01:19 PM
    • Replies: 0
    • Views: 132
    05-18-2016, 01:19 PM Go to last post
  23. Integrate different types of data from different studies?

    Hi, Is it possible to integrate different types of data from different studies? If yes, what precautions we must take? For example, let us...

    Started by GN1‎, 05-17-2016 01:43 AM
    biostatistics, research article
    • Replies: 1
    • Views: 173
    05-18-2016, 08:26 AM Go to last post
  24. Metal accumulation dependence on weight and pollution

    I'm working on metal accumulation in two landsnail species and it includes their kidneys and feet. I have concentrations of 7 metals in these organs...

    Started by Miii‎, 05-18-2016 04:42 AM
    • Replies: 1
    • Views: 194
    05-18-2016, 07:26 AM Go to last post
  25. I do not know how to calculate my sample size…

    Hello, can someone help me calculate my sample size and showing me the steps of how it should be done? I am going to do a study to see a...

    Started by Maria voltaren‎, 05-16-2016 04:37 AM
    sample size calculation
    • Replies: 0
    • Views: 153
    05-16-2016, 04:37 AM Go to last post
  26. Query about RRs and confounders

    Hi I am doing my head in over something very simple. Its more theoretical and I'm trying to work out a method. I am hoping someone can clarify...

    Started by statsanon‎, 05-15-2016 07:02 PM
    • Replies: 0
    • Views: 126
    05-15-2016, 07:02 PM Go to last post
  27. Question Safety or efficacy outcome?

    Dear friends, I got confused regarding outcome study I had to review. The primary outcome is: Time to the first occurrence of any of the...

    Started by wellfor‎, 05-14-2016 12:47 PM
    efficacy, outcome, safety
    • Replies: 0
    • Views: 145
    05-14-2016, 12:47 PM Go to last post
  28. Statistical test for proportions (values' range: 0-1)

    I am trying to compare mass spec data from 3 different conditions. For each protein I detected in my samples I have 3 values/condition (from 3...

    Started by jalbertortega‎, 05-13-2016 12:54 PM
    • Replies: 1
    • Views: 173
    05-14-2016, 09:10 AM Go to last post
  29. chi-square test

    Hi, can somone help me with doing a Chi-square test or Yates corrected chi-square test of the data file attached. I dont get it, or is the test...

    Started by Anne3‎, 05-12-2016 07:33 AM
    • Replies: 0
    • Views: 184
    05-12-2016, 07:33 AM Go to last post
  30. 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: 1
    • Views: 204
    05-11-2016, 12:33 AM Go to last post
  31. Repeated measures with one between subject and two within subject factors

    I have measured plasma cortisol levels in blood samples collected at an interval of 1 hour over a period of 24 hours in 10 male and female animals...

    Started by Bharath‎, 05-02-2016 06:05 PM
    • Replies: 2
    • Views: 299
    05-08-2016, 08:27 PM Go to last post
  32. Bootstrap strange estimate

    Hello everyone, I'm a statistical novice, I would like your help. I'm analyzing non-normally distributed variables. To develop the confidence...

    Started by andrew_fg‎, 05-06-2016 12:52 PM
    • Replies: 5
    • Views: 280
    05-06-2016, 06:40 PM Go to last post
  33. 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: 2
    • Views: 267
    05-05-2016, 01:16 PM Go to last post
  34. should I include a table with non significant results of Z proportion tests

    I am writing a manuscript and have a table with ONLY non significant Z proportion test results. I am wondering whether to omit this table although it...

    Started by Moranke‎, 05-02-2016 03:34 AM
    • Replies: 1
    • Views: 171
    05-05-2016, 07:26 AM Go to last post
  35. 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: 450
    04-26-2016, 06:06 PM Go to last post
  36. 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: 179
    04-26-2016, 01:21 PM Go to last post
  37. 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: 202
    04-24-2016, 05:57 PM Go to last post
  38. 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: 138
    04-24-2016, 06:50 AM Go to last post
  39. 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: 368
    04-15-2016, 02:31 AM Go to last post
  40. 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: 248
    04-13-2016, 03:45 AM Go to last post
  41. 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: 320
    04-08-2016, 07:19 PM Go to last post
  42. 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: 290
    04-06-2016, 02:56 PM Go to last post
  43. 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: 376
    03-29-2016, 03:36 PM Go to last post
  44. 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: 200
    03-29-2016, 12:58 PM Go to last post
  45. 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: 743
    03-28-2016, 03:21 PM Go to last post
  46. 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: 180
    03-28-2016, 12:39 PM Go to last post
  47. 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: 316
    03-25-2016, 02:47 AM Go to last post
  48. 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: 243
    03-23-2016, 05:25 PM Go to last post
  49. 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: 434
    03-20-2016, 11:56 AM Go to last post
  50. 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: 252
    03-18-2016, 11:39 AM Go to last post
  51. 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: 290
    03-17-2016, 11:30 AM Go to last post
  52. 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: 211
    03-17-2016, 09:00 AM Go to last post
  53. 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: 533
    03-16-2016, 07:53 PM Go to last post
  54. 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: 253
    03-16-2016, 02:22 PM Go to last post
  55. 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: 232
    03-16-2016, 09:09 AM Go to last post
  56. 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: 307
    03-12-2016, 06:00 AM Go to last post
  57. 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: 287
    03-11-2016, 12:43 PM Go to last post
  58. 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: 178
    03-11-2016, 09:07 AM Go to last post
  59. 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: 153
    03-11-2016, 07:48 AM Go to last post
  60. 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: 693
    03-06-2016, 09:49 PM Go to last post

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