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Forum: Biostatistics

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

  1. What test to use?

    Hey there, My first post here. I'm currently doing a course in uni which just goes through basic statistics and research methods. I am, however,...

    Started by 1337H4XXOR‎, 09-22-2012 08:57 PM
    • Replies: 2
    • Views: 1,545
    09-27-2012, 08:17 AM Go to last post
  2. need help regarding statistical methods for a project :(

    hi all, i have been tasked to do a biostats project and really need some advice from all the great biostatisticians out there! i have two...

    Started by yznahc‎, 09-25-2012 04:55 AM
    • Replies: 6
    • Views: 1,338
    09-25-2012, 06:12 AM Go to last post
  3. comparing change from baseline (two treatment groups, binomial data)

    I am comparing the effectiveness of a vaccine in reducing the prevalence of the targeted protein. I have baseline data (before the vaccine was even...

    Started by gopher‎, 09-24-2012 09:37 PM
    binomial, longitudinal, rct
    • Replies: 3
    • Views: 4,309
    09-25-2012, 05:58 AM Go to last post
  4. Which test / model to use ?

    Hello I need help choosing the most appropriate test to use: I have 3 groups of treatments, one is the new therapy, one is an active control...

    Started by Yankel‎, 09-20-2012 08:46 AM
    • Replies: 10
    • Views: 2,575
    09-24-2012, 07:37 AM Go to last post
  5. Whether to interpret based on descriptive or infferential statistics in present case?

    In our study which is already completed, I have three groups: Drug A(n=87), Drug B(=62) and Drug C(n=5). The Shapiro-Wilk test, Histograms and...

    Started by saurin‎, 09-14-2012 03:56 AM
    descriptive statistics, nonparametric statistics
    • Replies: 2
    • Views: 1,850
    09-23-2012, 07:13 AM Go to last post
  6. regression analysis

    hi. i need advise on how to do regression analysis with a discrete dependent variable and a number of dichotomous and continuous independent...

    Started by Herdie‎, 09-21-2012 12:34 AM
    dependent var, dichotomous, discrete, regression
    • Replies: 2
    • Views: 1,827
    09-21-2012, 09:02 AM Go to last post
  7. Question Weighting multiple responses vs single responses

    Hi, I am coding and summing the number of same/similar answers to a semi-open-ended question. While most respondents gave a single response, some...

    Started by csglass‎, 09-20-2012 03:30 PM
    • Replies: 1
    • Views: 2,165
    09-21-2012, 08:46 AM Go to last post
  8. Sample size formulas

    Hello, I find it difficult to find online the formulas for calculating sample sizes for: 1. ANOVA (k means) 2. Mann Whitney U test 3. Non...

    Started by NN_STAT‎, 09-20-2012 02:48 AM
    • Replies: 5
    • Views: 2,709
    09-20-2012, 02:30 PM Go to last post
  9. Confidence Level for device tests in fda

    Hello, I want to know what confidence level is required to be considered for proving a medicine or device is good and it will be great if anyone can...

    Started by expert4knowledge‎, 09-12-2012 03:01 AM
    • Replies: 1
    • Views: 1,608
    09-20-2012, 04:56 AM Go to last post
  10. Please help with study design

    Hello everyone, This is my first post and I really hope someone can help me. I have decided to compare three surgical pathways by collecting data...

    Started by Sir Gillies‎, 09-18-2012 12:37 PM
    • Replies: 2
    • Views: 2,110
    09-19-2012, 07:08 AM Go to last post
  11. Interpreting Cox proportional hazards

    I ran a simple cox proportional hazards survival analysis in R using the coxph function in the survival package. For 3 of 9 parameters, the p value...

    Started by carbrae‎, 09-12-2012 04:17 PM
    • Replies: 2
    • Views: 2,875
    09-17-2012, 02:20 PM Go to last post
  12. Correction for multiple comparisons applied to Chi2 value rather than p-value

    Hi, I am calculating hundreds of Chi2 and I correct for multiple corrections. The script I am using has a threshold at 400 for the Chi2 value beyond...

    Started by mousme‎, 09-06-2012 04:03 AM
    • Replies: 8
    • Views: 3,587
    09-17-2012, 01:44 PM Go to last post
  13. Sample size calculations for a study

    Hello I need some advice regarding sample size calculations. I need to calculate a sample size for a study testing a new drug. In the study...

    Started by NN_STAT‎, 09-15-2012 10:53 AM
    • Replies: 0
    • Views: 1,488
    09-15-2012, 10:53 AM Go to last post
  14. [Marine Biology] ANOVA (with unequal variances) statistical test?

    I have a pretty complicated data set that I don't know where to start. We sampled intertidal snails through an observation method, at two...

    Started by Bannana‎, 09-13-2012 07:30 PM
    anova, stats, t-test
    • Replies: 8
    • Views: 2,449
    09-14-2012, 01:04 AM Go to last post
  15. Comparing treatments over time - which test?

    Hi, I have been trying to find the effect of different treatments on fruit decay. The experiment: Fruit was monitored for degradation over a...

    Started by Elly‎, 09-11-2012 10:27 AM
    biological statistics, over time
    • Replies: 4
    • Views: 3,661
    09-13-2012, 10:40 AM Go to last post
  16. Comparing two methods to measure disease severity

    I am testing a new, fast method to score disease severity in an animal model of a human disease. M appears to be less sensitive than the gold...

    Started by kureot‎, 09-11-2012 01:15 PM
    confidence intervals, correlation analysis, dunnett t test, effect size, sensitivity analysis
    • Replies: 8
    • Views: 4,768
    09-12-2012, 07:20 PM Go to last post
  17. Pseudo-time lapse experiment: repeated measures ANOVA??

    I am measuring disease severity, using 5 different types of measurements, in animals treated with drug X, over multiple timepoints. The measurements...

    Started by kureot‎, 09-11-2012 01:47 PM
    correlation analysis, dunnett t test, repeated measures anova, time dependence
    • Replies: 0
    • Views: 2,315
    09-11-2012, 01:47 PM Go to last post
  18. This is a nightmare data set

    I'll make this brief so there is not too much confusion. I am looking for guidance and advice and generally just to bounce ideas of you guys. We...

    Started by bugman‎, 04-02-2012 04:36 AM
    • Replies: 7
    • Views: 3,775
    09-09-2012, 10:22 AM Go to last post
  19. clinical trials phase I question on probability of a trial stopping (MTD)

    I am given that the P(toxicity given dose) is a logistic function. The model to find the MTD is to first try 2 subjects at Dose 1, and if none...

    Started by lbragrl79‎, 09-08-2012 09:02 PM
    • Replies: 0
    • Views: 1,683
    09-08-2012, 09:02 PM Go to last post
  20. ROC curve analysis

    My question is whether i can apply a ROC curve analysis when I have paired samples i.e., the dichotomous variable 1/0 that identifies pathological...

    Started by dbpanag‎, 09-06-2012 08:18 AM
    • Replies: 3
    • Views: 2,189
    09-07-2012, 11:21 AM Go to last post
  21. MANOVAs dependent variables

    Hi everyone, I was doing a MANOVA and realised that some of my dependent variables are continuous and some are categorical (with values that are...

    Started by ozsunny2‎, 09-07-2012 04:00 AM
    • Replies: 0
    • Views: 2,124
    09-07-2012, 04:00 AM Go to last post
  22. Subtype of ANOVA to be used

    Hi everyone, I'm struggling a bit in trying to figure out what type of anova to use with my dataset. Essentially I have 10 patients implanted...

    Started by ozsunny2‎, 09-07-2012 02:51 AM
    • Replies: 1
    • Views: 992
    09-07-2012, 02:58 AM Go to last post
  23. Question Help to determine the correct statistical method (non-parametric MANOVA?)

    I can perform very basic statistics, but I have a serious problem with figuring out what to use in this case. I'm using R (within R Studio) since it...

    Started by laura_b‎, 09-04-2012 12:20 PM
    • Replies: 0
    • Views: 2,340
    09-04-2012, 12:20 PM Go to last post
  24. Test selection help for multivariate response and predictors

    I need help determining what method would be applicable to the following situation. There are 2 chemicals, A and B. Also, there are two organisms,...

    Started by jst04004‎, 08-31-2012 01:45 PM
    help me!, manova, multivariate, regression, response
    • Replies: 1
    • Views: 1,529
    08-31-2012, 02:22 PM Go to last post
  25. Question How to use nonparametric test with repeated measurements and many factors?

    Hi, I am investigating the effect of treatment A and B in two different groups of mice (Group A and group B). The outcome is continous (ug...

    Started by Amana‎, 08-27-2012 01:42 PM
    • Replies: 3
    • Views: 3,382
    08-28-2012, 09:03 AM Go to last post
  26. Heterogeneity test in meta-analysis

    Hi everyone, I am trying to do a meta-analysis of ecological data. I would like to do a formal test of heterogeneity between subgroups of a...

    Started by qdread‎, 08-27-2012 08:23 AM
    • Replies: 0
    • Views: 2,752
    08-27-2012, 08:23 AM Go to last post
  27. which testing should i do?

    I have counted bees on four different types of field margins, i have three locations where the field margins where grouped together. What i now...

    Started by pieter vanreamdonck‎, 08-03-2012 12:54 PM
    • Replies: 5
    • Views: 1,986
    08-23-2012, 02:53 AM Go to last post
  28. Test selection for a ‘marks out of 10’ quiz: Binomial, Fisher, meta-analysis, or ?

    Hello, I have been testing a type of depth of anaesthesia monitor. It involves listening to the EEG (i.e. it’s an electroencephalophone). It’s...

    Started by johnglen‎, 08-19-2012 12:55 PM
    • Replies: 0
    • Views: 19,230
    08-19-2012, 12:55 PM Go to last post
  29. Non-parametric alternative to repeated-measures ANOVA with a between-subjects factor?

    Hello, I'm trying to do a repeated-measures ANOVA but my data is likely violating the multivariate normality assumption. My question is: Does...

    Started by PHO_M‎, 08-15-2012 04:19 PM
    • Replies: 4
    • Views: 58,830
    08-17-2012, 07:50 AM Go to last post
  30. Gene expression analysis - FDR and p-values

    Hi, I'm using Affymetrix microarrays to check if there exist some differences in the gene expression of two group of animals that have been...

    Started by jma‎, 08-07-2012 09:30 AM
    • Replies: 4
    • Views: 15,778
    08-17-2012, 04:34 AM Go to last post
  31. Fixed effects vs. Random Effects

    Hi we had 5 investigators 1)hand out 100 surveys and 2)record a certain feature of each of the 100 subjects. That feature that they recorded is the...

    Started by wuzzy‎, 08-15-2012 11:27 AM
    fixed, random
    • Replies: 1
    • Views: 1,896
    08-16-2012, 08:32 PM Go to last post
  32. Which test should I use to compare these two groups?

    Hi everybody. I have two groups of doctors, group A and group B. I'm trying to see if there is any statistical difference between them in their...

    Started by MadDoc‎, 08-16-2012 07:11 AM
    • Replies: 7
    • Views: 2,024
    08-16-2012, 02:58 PM Go to last post
  33. Bisulfite Sequencing - Is a t-test enough?

    Hey everybody, I am a plant molecular biologist doing some bisulfite sequencing. I am currently using a t-test on my data, but I feel like that...

    Started by diowulf‎, 08-13-2012 03:25 PM
    • Replies: 0
    • Views: 1,689
    08-13-2012, 03:25 PM Go to last post
  34. Post Job: Health Economist/Economitrician/Biostatistician Required

    Health Economist Introduction This is an opportunity to work for an international company specialising in Health Economics, Patient-Reported...

    Started by abhijeetroy‎, 08-13-2012 05:37 AM
    biostatistician, career, econometrics, health economist, jobs
    • Replies: 0
    • Views: 1,469
    08-13-2012, 05:37 AM Go to last post
  35. Post Estimates

    Compare point estimate to interval estimate

    Started by 0302‎, 08-10-2012 04:21 AM
    • Replies: 2
    • Views: 1,567
    08-10-2012, 07:14 PM Go to last post
  36. Durbin-Watson Test

    Hi, I'm looking to analyse some vigilance data from monkeys. The data at the moment comes from 5minute samples, but these are separated depending...

    Started by mr_bennyc‎, 08-09-2012 07:19 AM
    • Replies: 3
    • Views: 2,492
    08-09-2012, 11:49 AM Go to last post
  37. ANCOVA violating assumptions

    Hi, The data I'm looking to analyse is vigilance data from monkeys. I need to investigate which factors affect the different types of vigilance....

    Started by mr_bennyc‎, 08-08-2012 12:02 PM
    ancova, general linear model, normality, variance
    • Replies: 0
    • Views: 1,680
    08-08-2012, 12:02 PM Go to last post
  38. Forecasting "half-time", which method?

    My problem: My data is a time-series of watersamples taken daily. The water have a concentration of a toxic pollution and I want to forecast the...

    Started by sellingforsale‎, 08-08-2012 08:11 AM
    • Replies: 0
    • Views: 1,108
    08-08-2012, 08:11 AM Go to last post
  39. Sample size when comparing 3 groups (proportions)

    Problem: I use a common clinical specimen divided equally into two sets with each set to test 3 culture media for growth of a certain organism after...

    Started by tapyboy‎, 08-06-2012 03:48 AM
    3 groups, 3 proportions, comparing percentages, sample size
    • Replies: 0
    • Views: 2,547
    08-06-2012, 03:48 AM Go to last post
  40. Am I allowed to pool groups for GLM?

    Here is my problem: I am doing a stability study, for which I have several lots on different storage temperatures. In order to asses the...

    Started by gamadeus‎, 07-13-2012 12:43 PM
    • Replies: 3
    • Views: 1,803
    08-03-2012, 09:15 AM Go to last post
  41. Discrepencies between SPSS and SAS

    Does anyone know why there are differences in results when performing Kaplan Meier survival analysis tests in SPSS and SAS. The values do not match...

    Started by pauljj‎, 07-31-2012 08:46 AM
    difference, kaplan meier, sas, spss, survival analysis
    • Replies: 8
    • Views: 2,296
    08-02-2012, 03:28 PM Go to last post
  42. biostatistics - command to use for association of fiber intake and cancer

    hi everyone can you help me which test i should use ? purpose is to determine the association of intake of dietary-fiber (3 different types of...

    Started by floritta‎, 07-10-2012 04:58 AM
    • Replies: 1
    • Views: 1,634
    08-02-2012, 07:25 AM Go to last post
  43. Cox Proportional Hazards Regression

    Hi, I am hoping someone can help me with which model (frailty, strata or cluster) I should use for my data. I have paired data so I need to take...

    Started by MJ77‎, 07-23-2012 03:01 AM
    cox regression, paired data, survival analysis, time to event
    • Replies: 1
    • Views: 2,623
    08-02-2012, 07:25 AM Go to last post
  44. Summing Confidence Intervals?

    Hello, I have calculated mean concentrations of various environmental chemicals in a population. These chemicals fall into different classes...

    Started by AMac‎, 07-30-2012 03:58 PM
    confidence intervals, means
    • Replies: 2
    • Views: 7,092
    08-01-2012, 07:08 PM Go to last post
  45. Univariate or Multivariate?

    Hi My data is on two equal groups of patients. The two groups have roughly equal proportions of males/females. A blood sample was obtained form each...

    Started by ASSAN‎, 07-15-2012 12:49 PM
    blood tests, multivariate, non-parametric tests, npmanova, univariate
    • Replies: 2
    • Views: 1,762
    08-01-2012, 06:58 PM Go to last post
  46. Sample size calculations

    Hi all, I know nothing about sample size calculations, and always feel that this is an area I am lacking in. In general I work with data that has...

    Started by duskstar‎, 07-23-2012 09:04 AM
    • Replies: 5
    • Views: 2,426
    07-31-2012, 08:32 AM Go to last post
  47. MANOVAs

    Hi, I’ve performed a MANOVA but cannot perform a box test (because I have fewer subjects per factor than dependent variables). I was wondering if...

    Started by bs10cjg‎, 07-31-2012 06:25 AM
    • Replies: 0
    • Views: 1,442
    07-31-2012, 06:25 AM Go to last post
  48. Nested/Repeated Comparisons-What test should I use?

    Hi! I am having trouble to decide what statistical test to use on my data because I have one factor grouped within another. Here is my...

    Started by WhackyWolbachia‎, 07-10-2012 05:53 AM
    experimental design, microarray, multiple comparisons, nested analysis
    • Replies: 3
    • Views: 1,727
    07-30-2012, 10:45 AM Go to last post
  49. Characterizing a population

    Hello, I have data regarding some new blood test. I have a large sample of 450 patients, all healthy, and I would like to characterize the...

    Started by NN_STAT‎, 07-24-2012 04:06 AM
    • Replies: 6
    • Views: 2,819
    07-28-2012, 07:56 PM Go to last post
  50. Which test to use?

    Hi everyone, I'm working on analyzing some data right now but I'm not sure if I'm even approaching this correctly. I have a master set of data that I...

    Started by lembdan‎, 07-27-2012 08:56 AM
    • Replies: 0
    • Views: 1,358
    07-27-2012, 08:56 AM Go to last post
  51. How to compare paired, non-normal and GROUPED data?

    Hi, community, I'm trying to solve this issue using free software on Mac OS X and Ubuntu, namely PSPP (SPSS-compatible), Gnumeric, LibreOffice,...

    Started by Cubytus‎, 07-27-2012 01:44 AM
    • Replies: 0
    • Views: 1,901
    07-27-2012, 01:44 AM Go to last post
  52. How to compare repeated measurements

    Okay, I have one group of patients. This is a hypothetical example: drug A and B are drugs that decrease puls rate. After application of...

    Started by med1234‎, 06-23-2012 05:31 PM
    • Replies: 6
    • Views: 2,937
    07-16-2012, 10:15 PM Go to last post
  53. Variance used as dependent variable in logistic regression

    Hi all, I'm investigating the factors that contribute to high or low variability in the greenness index of a grassland area over the course of 10...

    Started by Walker‎, 07-10-2012 11:21 AM
    • Replies: 2
    • Views: 1,669
    07-12-2012, 04:50 PM Go to last post
  54. FDR and FWER

    Hello, I was looking for some online material about False Discovery Rate and Family wise Error Rate. I found a nice lecture that consisted of 2...

    Started by NN_STAT‎, 02-11-2012 09:20 AM
    • Replies: 5
    • Views: 8,335
    07-12-2012, 06:38 AM Go to last post
  55. Propensity Score Matching

    Hello, I have retrospective non-randomised data and wish to investigate the relationship between blood transfusions (2 treatment groups :...

    Started by macguilm‎, 07-09-2012 07:56 AM
    propensity score matching
    • Replies: 3
    • Views: 2,103
    07-09-2012, 09:04 AM Go to last post
  56. Understanding how PFS and other "survival" outcomes are actually defined

    Hello, I am trying to better understand how are end points in clinical trials defined when Kaplan-Meier method/log rank test is used. I met this...

    Started by Markica85‎, 07-05-2012 03:53 PM
    • Replies: 0
    • Views: 1,782
    07-05-2012, 03:53 PM Go to last post
  57. groups clustering

    Hello everybody, I was wondering about a method to lump a dataset of 20 groups of subjects, each group characterized by a specific mean age, stand...

    Started by marco77‎, 07-05-2012 12:29 PM
    • Replies: 0
    • Views: 1,529
    07-05-2012, 12:29 PM Go to last post
  58. test to evaluate paired data with 2 ind variables?

    Hello, I am conducting a basic preference test experiment to determine whether subjects spend a longer time investigating sample A vs. B, and for...

    Started by Els22‎, 07-02-2012 12:13 AM
    • Replies: 0
    • Views: 1,268
    07-02-2012, 12:13 AM Go to last post
  59. Impact of age and treatment approach on incidence rates of adverse outcome

    In a meta-analysis looking at the impact of age on the incidence of an adverse outcome following treatment for "X", which effect sizes and...

    Started by mhill6‎, 07-01-2012 01:21 AM
    • Replies: 0
    • Views: 1,015
    07-01-2012, 01:21 AM Go to last post
  60. Testing a drug's effect on survival across multiple distinct studies

    I have survival and other data for between ~1000 patients from different studies with indications varying from organ transplantation to cancer....

    Started by ieee529‎, 06-30-2012 09:26 AM
    • Replies: 0
    • Views: 1,471
    06-30-2012, 09:26 AM Go to last post

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