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Forum: Biostatistics

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

  1. starting in biostats and need to analyse clinical data. how to begin.

    Hello everybody I am a very beginer in stats and in using SPSS. I need to analyse some clinical data. I want to know please if this is a good...

    Started by Stat_begi‎, 07-22-2016 02:21 PM
    • Replies: 1
    • Views: 109
    07-22-2016, 03:54 PM Go to last post
  2. Which statistical approach?

    Dear all, I am a biologist with a very poor statistical knowledge so please excuse me if my question is not very well formulated- I am doing my best...

    Started by Nessie‎, 07-18-2016 08:57 AM
    gene related
    • Replies: 4
    • Views: 222
    07-18-2016, 09:41 AM Go to last post
  3. Correct analysis of crossover trials

    Hi everybody I was wondering if anyone here had any expertise regarding analysis of crossover trials. I'm writing my thesis at the moment and...

    Started by TNK78‎, 07-18-2016 06:56 AM
    analysis, crossover trial, treatment sequence
    • Replies: 1
    • Views: 80
    07-18-2016, 08:29 AM Go to last post
  4. Author's interpretation of Odds Ratio and Confidence intervals

    Hi all, Having some difficulty understanding the results of this paper I am including in a review. It compares the effects of 3 interventions...

    Started by crkc‎, 07-16-2016 07:23 AM
    confidence interval, intervention, odds ratio, significance
    • Replies: 1
    • Views: 113
    07-16-2016, 08:16 AM Go to last post
  5. What does a mean probability mean?

    Hi all. If each case in a dataset is assigned a probability of a certain event having occurred (based on their own individual data) and I...

    Started by blue11‎, 07-13-2016 06:09 PM
    • Replies: 1
    • Views: 137
    07-13-2016, 07:05 PM Go to last post
  6. Computing age and gender standardised mean BMI

    Hi, I'll appreciate a lot if someone could tell me how to compute age and gender standardised mean BMI in stata. Thanks. ZZ

    Started by Zain Zaid‎, 07-10-2016 08:20 PM
    • Replies: 0
    • Views: 213
    07-10-2016, 08:20 PM Go to last post
  7. Please help interpret cross-sectional study results (odds ratio, relevant risk, etc.)

    I'm trying to help my wife with some statistics. She's looking to see if people with Removable Dentures (RD) have a higher prevalence of Combination...

    Started by jbbuck‎, 07-08-2016 04:32 PM
    confidence interval, cross-sectional study, odds ratio, relative risk
    • Replies: 1
    • Views: 181
    07-09-2016, 03:35 AM Go to last post
  8. Lightbulb 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...

    Started by rony443‎, 07-08-2016 02:01 AM
    power analysis, sample size
    • Replies: 2
    • Views: 143
    07-08-2016, 10:54 AM Go to last post
  9. SPSS, descriptive statistics, crosstabs, risk

    the problem has been solved. thanks

    Started by Menekse‎, 07-07-2016 03:36 AM
    • Replies: 0
    • Views: 127
    07-07-2016, 03:36 AM Go to last post
  10. Parallel Bioequivalence Study Sample Size

    I need to calculate the required sample size given the following information: Power=80% Coefficient of variation for Cmax and AUC = 40% True...

    Started by gopher‎, 07-04-2016 03:26 AM
    bioequivalence, sample size calculation
    • Replies: 0
    • Views: 212
    07-04-2016, 03:26 AM Go to last post
  11. Question How to prove two methods are “similar”?

    We are testing two imaging machines. One of the machines has been validated numerous times. However, we built the new machine and we need to prove...

    Started by yolo123‎, 07-01-2016 09:40 AM
    physics, research, statistics, validation
    • Replies: 1
    • Views: 249
    07-01-2016, 10:40 AM Go to last post
  12. 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: 381
    06-29-2016, 04:18 AM Go to last post
  13. 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: 273
    06-25-2016, 04:05 PM Go to last post
  14. 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: 431
    06-24-2016, 10:10 AM Go to last post
  15. 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: 174
    06-24-2016, 02:45 AM Go to last post
  16. 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: 367
    06-22-2016, 05:34 PM Go to last post
  17. 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: 316
    06-21-2016, 06:50 AM Go to last post
  18. 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: 167
    06-20-2016, 12:23 PM Go to last post
  19. 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: 507
    06-14-2016, 06:55 PM Go to last post
  20. 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: 506
    06-11-2016, 06:13 PM Go to last post
  21. 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: 273
    06-10-2016, 02:02 PM Go to last post
  22. 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: 229
    06-02-2016, 11:44 PM Go to last post
  23. 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: 228
    06-01-2016, 06:24 AM Go to last post
  24. 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: 129
    05-31-2016, 03:59 PM Go to last post
  25. 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: 340
    05-26-2016, 06:49 AM Go to last post
  26. 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: 139
    05-25-2016, 04:03 AM Go to last post
  27. 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: 217
    05-24-2016, 01:55 PM Go to last post
  28. 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: 280
    05-24-2016, 09:03 AM Go to last post
  29. 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: 380
    05-23-2016, 08:12 AM Go to last post
  30. 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: 178
    05-22-2016, 12:47 PM Go to last post
  31. 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: 355
    05-20-2016, 04:07 AM Go to last post
  32. 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: 292
    05-19-2016, 02:27 PM Go to last post
  33. 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: 176
    05-18-2016, 01:19 PM Go to last post
  34. 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: 212
    05-18-2016, 08:26 AM Go to last post
  35. 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: 231
    05-18-2016, 07:26 AM Go to last post
  36. 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: 204
    05-16-2016, 04:37 AM Go to last post
  37. 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: 157
    05-15-2016, 07:02 PM Go to last post
  38. 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: 189
    05-14-2016, 12:47 PM Go to last post
  39. 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: 214
    05-14-2016, 09:10 AM Go to last post
  40. 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: 245
    05-12-2016, 07:33 AM Go to last post
  41. 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: 240
    05-11-2016, 12:33 AM Go to last post
  42. 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: 333
    05-08-2016, 08:27 PM Go to last post
  43. 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: 335
    05-06-2016, 06:40 PM Go to last post
  44. 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: 309
    05-05-2016, 01:16 PM Go to last post
  45. 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: 202
    05-05-2016, 07:26 AM Go to last post
  46. 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: 493
    04-26-2016, 06:06 PM Go to last post
  47. 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: 209
    04-26-2016, 01:21 PM Go to last post
  48. 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: 238
    04-24-2016, 05:57 PM Go to last post
  49. 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: 171
    04-24-2016, 06:50 AM Go to last post
  50. 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: 401
    04-15-2016, 02:31 AM Go to last post
  51. 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: 269
    04-13-2016, 03:45 AM Go to last post
  52. 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: 352
    04-08-2016, 07:19 PM Go to last post
  53. 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: 331
    04-06-2016, 02:56 PM Go to last post
  54. 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: 413
    03-29-2016, 03:36 PM Go to last post
  55. 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: 228
    03-29-2016, 12:58 PM Go to last post
  56. 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: 883
    03-28-2016, 03:21 PM Go to last post
  57. 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: 214
    03-28-2016, 12:39 PM Go to last post
  58. 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: 353
    03-25-2016, 02:47 AM Go to last post
  59. 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: 271
    03-23-2016, 05:25 PM Go to last post
  60. 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: 476
    03-20-2016, 11:56 AM Go to last post

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