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Forum: Biostatistics

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

  1. Mixture models

    Hi, I've fitted a two-component normal mixture model to some genetic data. I now need to compare this to a single component model but I'm not sure...

    Started by Sezmarelda‎, 08-17-2011 03:55 AM
    • Replies: 1
    • Views: 2,561
    08-17-2011, 09:19 AM Go to last post
  2. Logistic Regression

    Hello, I have a a little problem, and not sure about the results. I have a machine that is supposed to diagnose ill people. The machine will...

    Started by NN_STAT‎, 08-15-2011 11:39 AM
    • Replies: 6
    • Views: 2,902
    08-16-2011, 06:39 AM Go to last post
  3. Please help a surgeon with p-values etc in his presentation!

    Dear all, I am presenting at an international presentation on the topic of bariatric surgery in a specific subpopulation. There is a lot of...

    Started by Jeremy Lynch‎, 08-14-2011 06:44 AM
    • Replies: 7
    • Views: 3,078
    08-15-2011, 11:40 AM Go to last post
  4. statistics technique for varying symptoms with nutrient

    I am trying to study a patient symptom levels vs one or more nutriceuticals they are taking. I'm wondering what technique I would use if the nutrient...

    Started by Daniel Savage‎, 08-14-2011 08:41 PM
    • Replies: 0
    • Views: 1,635
    08-14-2011, 08:41 PM Go to last post
  5. LOD and LOQ calculation

    How to calculate LOD and LOQ for viral assays (poisson method). The data and reference is attached. Data is available on page number 5. If you just...

    Started by Asad Ahmad‎, 08-12-2011 12:54 AM
    • Replies: 0
    • Views: 4,715
    08-12-2011, 12:54 AM Go to last post
  6. Creating "score" --> by adding ORs?

    I have created a prognostic model using logistic regression. It predicts diabetes based on 6 independent variables (age, sex BMI, etc). I...

    Started by chipsens‎, 08-09-2011 11:34 AM
    logarithmic, logistic regression, odds ratio, regression equation, score
    • Replies: 1
    • Views: 2,442
    08-11-2011, 02:21 PM Go to last post
  7. best methods for nutrient vs symptoms

    I'm tracking a few different nutrients like quercetin, coq vs patient symptoms for an online project written in Unity3d (uses javascript). I've been...

    Started by Daniel Savage‎, 08-11-2011 11:41 AM
    • Replies: 0
    • Views: 1,369
    08-11-2011, 11:41 AM Go to last post
  8. Exclamation Help, I don't know what method did I use in my final paper

    Sorry for my english, it's not my mother tongue. Yeah, i know i'm stupid, but I really don't know what did I use. In my notebook it says t-test,...

    Started by sovac‎, 08-11-2011 03:12 AM
    • Replies: 2
    • Views: 2,682
    08-11-2011, 09:36 AM Go to last post
  9. What method should I use? Regression? ANCOVA?

    Hello, I am confused, I think that the problem is really simple, but somehow cannot get hold of this. First, the simpler question. I have...

    Started by jw3‎, 08-10-2011 01:46 AM
    • Replies: 2
    • Views: 2,609
    08-11-2011, 07:37 AM Go to last post
  10. Compare 2 Shannon index for a single site in two different years

    Hello (and sorry for my english), I realize for an NGO in Madagascar, a survey for the monitoring of amphibians in a natural reserve. In my...

    Started by kenpachi13‎, 08-11-2011 04:02 AM
    • Replies: 0
    • Views: 2,758
    08-11-2011, 04:02 AM Go to last post
  11. Sample Size Calculations

    Hello, Does anyone here knows the way of calculating a sample size according to a desired sensitivity and specificity rates ? I have two...

    Started by NN_STAT‎, 08-11-2011 02:24 AM
    • Replies: 0
    • Views: 1,991
    08-11-2011, 02:24 AM Go to last post
  12. Unbalanced sampling is a problem in [R]

    Hi All, I am trying to run an ANCOVA in R, however, my sampling design was far from balanced. In R, I've heard that this is problematic, since the...

    Started by Curseit‎, 08-09-2011 01:13 PM
    • Replies: 3
    • Views: 4,264
    08-09-2011, 02:10 PM Go to last post
  13. Question about a study

    So, I'm reading a study about drug being used to induce remission of a disease. There are two treatments, the drug and placebo. They rate the...

    Started by pharmer‎, 08-08-2011 11:23 PM
    • Replies: 4
    • Views: 2,828
    08-09-2011, 01:07 PM Go to last post
  14. What statistical approach should I take?

    I have 2 population (G1 and G2). The 2 population are equal in terms of the total number of individuals. They have the same number of markers/loci....

    Started by mike_electron‎, 08-07-2011 01:39 PM
    • Replies: 2
    • Views: 2,328
    08-07-2011, 10:14 PM Go to last post
  15. wilcoxon rank sum test or t-test?

    Hello, I have a question for my analysis and reporting. For my analysis, simply said I measured the time needed to achieve sufficient pain...

    Started by noob‎, 08-03-2011 02:12 PM
    • Replies: 8
    • Views: 19,619
    08-07-2011, 07:04 AM Go to last post
  16. Trying to prove significant difference between algal biovolume data

    Hello everyone I would like if possible to ask a question regarding a part of the statistical analysis in my MSc project: Following the sampling...

    Started by manos1234‎, 08-04-2011 04:45 AM
    biovolume, non-parametric
    • Replies: 9
    • Views: 3,512
    08-05-2011, 02:59 AM Go to last post
  17. Determining a cut-off for groups in survival prediction


    Started by LAnn‎, 08-02-2011 11:00 AM
    • Replies: 6
    • Views: 4,813
    08-03-2011, 07:56 PM Go to last post
  18. What method shoudl I inthose cell biovolume data

    Hello everyone! I am wiring a masters project involving counting algae and I am having a difficulty finding what is the right method to do the...

    Started by manos1234‎, 08-03-2011 02:25 PM
    algae, biovolume, non-parametric, wilcoxon
    • Replies: 0
    • Views: 1,436
    08-03-2011, 02:25 PM Go to last post
  19. Exclamation Urgent_whether matched pairs need covariate analysis

    I am comparing genes expression between 2 groups of matched pairs. Other factors that may affect gene expression have been matched between each...

    Started by jiwu2573‎, 07-16-2011 04:57 AM
    • Replies: 2
    • Views: 3,553
    08-03-2011, 12:14 AM Go to last post
  20. Logistic Regression with huge coefficients

    Hi, I ran a logistic regression model, and got a regression coefficient of 1186.35 ! Obviously, it's not possible to calculate Odds Ratio with...

    Started by NN_STAT‎, 08-01-2011 02:52 AM
    • Replies: 1
    • Views: 3,227
    08-01-2011, 03:43 AM Go to last post
  21. logistic regression with air pollution data

    I am conducting a study to detect the impact of particulate matter air pollution on a health parameter but i do not know how to include the...

    Started by Maha‎, 07-29-2011 02:03 AM
    • Replies: 1
    • Views: 2,151
    07-30-2011, 07:07 AM Go to last post
  22. Pearson correlation in opthalmic data

    Hello, I have data on two eyes for 115 subjects and I want to see if their vision trait (such as visual acuity,macular edema,...) is each correlated...

    Started by LSH‎, 07-29-2011 02:42 PM
    • Replies: 0
    • Views: 1,602
    07-29-2011, 02:42 PM Go to last post
  23. Intra- and Interrater reliability of imaging findings

    Hi everyone, I'm having some difficulty deciding how best to analyze the data from a project. I had 4 radiologist read CT scans looking for...

    Started by Hugo‎, 07-24-2011 03:31 AM
    kappa, krippendorff's alpha, reliability, spss, weighted
    • Replies: 1
    • Views: 2,270
    07-28-2011, 02:35 PM Go to last post
  24. Cox Proportional Hazards Assumption Question

    I have a dataset of cancer cases from 1997 to 2007. I am performing a Cox Model on this set of cases. However, I just realized that mortality rates...

    Started by Kevin Matthews‎, 07-28-2011 01:53 PM
    cox, mortality, survival
    • Replies: 0
    • Views: 2,725
    07-28-2011, 01:53 PM Go to last post
  25. Question Genotyping using melting temperature data

    I am trying to assign genotypes to individuals from a population using melting temperature information. I am fairly certain that all individuals have...

    Started by ewelch‎, 07-26-2011 02:10 PM
    genotyping, melting curve analysis, melting temperature, molecular biology, population genetics
    • Replies: 0
    • Views: 1,628
    07-26-2011, 02:10 PM Go to last post
  26. Significance test for differences in baseline and re measurement rates

    Hi, I need help in knowing which test to perform with this analysis. I have two groups (lets say group A and B). A study was performed with...

    Started by nupur‎, 07-24-2011 04:20 PM
    biostatistics, statistic, t-test
    • Replies: 3
    • Views: 3,313
    07-25-2011, 06:09 PM Go to last post
  27. Wilcoxon Signed Rank Test Approriate?

    Below is an example of what type of data I am looking at. They are data of angle of flexion of an elbow healing from injury from different patients....

    Started by lyc83‎, 07-25-2011 09:48 AM
    • Replies: 4
    • Views: 3,502
    07-25-2011, 03:09 PM Go to last post
  28. Clinical Significant vs Statistical Significant

    Hi Guys, I read some strong criticism about "statistical significance". Some researchers claim that statistical significance is useless. in...

    Started by WeeG‎, 04-09-2011 07:33 AM
    • Replies: 8
    • Views: 11,833
    07-25-2011, 12:43 PM Go to last post
  29. Wilcoxon Rank Sum Test vs Van de Waerden Test

    Hi, Would anyone be able to explain the difference between the Wilcoxon Rank Sum Test vs Van de Waerden Test? Do they look at or analyze the same...

    Started by Koofy‎, 07-20-2011 12:53 AM
    van de waerden, wilcoxon
    • Replies: 6
    • Views: 8,310
    07-22-2011, 01:43 PM Go to last post
  30. Power/site analysis for cox proportional with categorial data

    Dear all, Since I didn't succeed solving my problem by google maybe one of you might have a solution to my problem: In order to evaluate whether a...

    Started by rolfh‎, 07-22-2011 11:43 AM
    • Replies: 0
    • Views: 2,290
    07-22-2011, 11:43 AM Go to last post
  31. swapping outcome and independent variables

    I have a bit of mental dilemma I am doing a survey investigating variables . The outcome variable is binary , and for simplicity's sake it is...

    Started by blowe46‎, 07-21-2011 10:39 AM
    • Replies: 6
    • Views: 4,156
    07-21-2011, 05:07 PM Go to last post
  32. Exclamation Another logistic regression queston

    Hi, I am analyzing data with polytomous outcome, and the predictor is in rate ratio. after run the logistic regression procedure, the result looks...

    Started by dinsya‎, 07-08-2011 04:09 AM
    • Replies: 3
    • Views: 2,222
    07-14-2011, 11:26 AM Go to last post
  33. Other's thoughts on Poisson regression

    Per the suggestions of fellow Talk stats members (& moderstors) I am working through Poisson regression. I came across an article Essentials of...

    Started by trinker‎, 07-13-2011 07:46 PM
    • Replies: 4
    • Views: 3,270
    07-14-2011, 11:16 AM Go to last post
  34. Weibull left censored is exponential?

    Hello, I have the following question. Let's assume that we want to study the time of a group of patient until they get a certain disease D. We...

    Started by giordano‎, 07-08-2011 04:01 AM
    • Replies: 4
    • Views: 2,759
    07-14-2011, 01:46 AM Go to last post
  35. Test of similar population distribution, or test of sample randomness?

    I have a sample of patient data (age 5-18) by census tract, and I know the underlying population distribution (age 5-18) by census tract. I want to...

    Started by danafer‎, 07-12-2011 04:12 PM
    pouplation distribution, sample randomness
    • Replies: 0
    • Views: 3,037
    07-12-2011, 04:12 PM Go to last post
  36. Question regarding Analysis of Molecular Variance (AMOVA)

    Hi, I have had problems running an AMOVA analysing allele frequencies on Arlequin. In the AMOVA I am observing allele frequency differences between...

    Started by rob180‎, 07-12-2011 07:36 AM
    • Replies: 0
    • Views: 2,093
    07-12-2011, 07:36 AM Go to last post
  37. Model Question

    I have the following question for my classwork: I have a set of about two hundred subjects that we planning to measure their pain during the start of...

    Started by Medic49‎, 07-10-2011 11:26 PM
    • Replies: 1
    • Views: 1,965
    07-11-2011, 09:45 PM Go to last post
  38. semi parametric statistic?

    can any one give me idea about what is semi parametric statistic?

    Started by Dr Bansari‎, 07-06-2011 01:55 PM
    • Replies: 5
    • Views: 3,052
    07-08-2011, 10:55 PM Go to last post
  39. Matched survival study

    How would you go about drawing a sample and analyzing this type of study?

    Started by fed1‎, 07-08-2011 07:57 PM
    • Replies: 0
    • Views: 1,898
    07-08-2011, 07:57 PM Go to last post
  40. Cyclical Data Transformation

    For data that may look linear but is in fact cyclical (time most commonly), is there like a sine function based data transformation that has been...

    Started by greg.neyman‎, 06-05-2011 01:55 PM
    • Replies: 9
    • Views: 5,820
    07-06-2011, 04:41 PM Go to last post
  41. The characteristics of a nested case-control study?

    Should all studies that compare the cases of a cohort with a sub-population of the non-cases be called nested case-control studies? Or would some of...

    Started by CarlAH‎, 07-03-2011 11:14 AM
    • Replies: 6
    • Views: 5,522
    07-04-2011, 07:02 PM Go to last post
  42. Sample Size for Logistic Regression

    Hello, I need to calculate the sample size for a logistic regression model, which I need to use for determining if a few variables can predict an...

    Started by NN_STAT‎, 07-04-2011 12:15 AM
    • Replies: 0
    • Views: 3,185
    07-04-2011, 12:15 AM Go to last post
  43. Confidence interval for risk

    Hi, In attachment, I join a table that I would like to replicate with our data. Is there any one that knows how to calculate the 95% CI. I...

    Started by cynan‎, 07-03-2011 06:57 AM
    • Replies: 2
    • Views: 2,089
    07-03-2011, 10:25 AM Go to last post
  44. Confidence intervals for survival estimates with combinations of risk factors

    Dear all, I have time-to-event data for patients with epilepsy. We have produced a parsimonious multivariable model for this event and therefore...

    Started by ljbcmshe‎, 06-29-2011 10:21 AM
    confidence interval, hazard, survival analysis
    • Replies: 2
    • Views: 1,642
    07-01-2011, 09:45 PM Go to last post
  45. Unhappy Clinical Dose Audit Analysis

    I have a database of records of medical exposures for various radiographic examinations and their respective Dose Area Product (DAP) measurements....

    Started by clownyj‎, 07-01-2011 06:23 AM
    • Replies: 0
    • Views: 1,467
    07-01-2011, 06:23 AM Go to last post
  46. What model?

    Hi there I am supposed to test two data points, both triplicates for significant difference. I am not sure whether to use a paired or unpaired...

    Started by Mark_S‎, 06-29-2011 10:43 AM
    • Replies: 2
    • Views: 1,888
    06-30-2011, 04:51 AM Go to last post
  47. Data fails homogeneity tests

    Hi all, I'm looking at how size of an insect is different between two treatments of prey and non-prey samples. Size of all samples increases with...

    Started by Curseit‎, 06-28-2011 04:08 PM
    • Replies: 2
    • Views: 2,898
    06-29-2011, 11:16 AM Go to last post
  48. Repeated Measures ANOVA?

    I am going through some data and am not convinced that the Statistical design recommended by a colleague is correct. I have two treatments, T1 and...

    Started by hwc007‎, 04-22-2011 03:15 PM
    • Replies: 2
    • Views: 2,870
    06-28-2011, 12:45 PM Go to last post
  49. GLM logistic regression with a post-hoc dimensional factor

    First, I apologise for the equation formatting; I'm new to the forum and I don't know the best way to enter equations. I am applying a linear...

    Started by waldog‎, 06-23-2011 10:59 AM
    • Replies: 1
    • Views: 1,904
    06-28-2011, 08:35 AM Go to last post
  50. Poisson regression

    I am looking at risk factors associated with infant deaths over 4 years at the state level comparing a black population to a reference group. Each...

    Started by RyanD‎, 06-21-2011 11:47 AM
    • Replies: 1
    • Views: 2,037
    06-25-2011, 03:54 PM Go to last post
  51. Help with interpreting a table

    Hello all, First of all I want to congratulate the moderators in maintaining this forum so well. I don't think I can maintain even my room so...

    Started by godsaveme‎, 06-24-2011 07:54 AM
    • Replies: 2
    • Views: 2,246
    06-25-2011, 01:28 PM Go to last post
  52. 2 methods proportional hazard in SPSS

    Goodafternoon, (Answers are welcome in English, Dutch and German) I have a question concerning how to test for the proportional hazard assumption,...

    Started by dllique‎, 06-23-2011 09:19 AM
    • Replies: 0
    • Views: 8,100
    06-23-2011, 09:19 AM Go to last post
  53. Can a cohort study have no control groups (is a clinical series study a cohort)?

    Hi AFAK a cohort study needs a matched control group. However, its definition doesn't necessitate a control group. Moreover, I have read some...

    Started by victorxstc‎, 05-25-2011 04:09 AM
    case series, clinical series, cohort
    • Replies: 5
    • Views: 21,874
    06-22-2011, 11:45 PM Go to last post
  54. Bacteria Death on surfaces

    Hi, I've got myself pretty confused with my stats... I've got experimental results from a study into bacterial death on wet surfaces. I had a...

    Started by Jonathon‎, 06-21-2011 10:50 AM
    • Replies: 0
    • Views: 2,687
    06-21-2011, 10:50 AM Go to last post
  55. Question One way ANOVA or Two way, Univariate or Multivariate

    Hey there, I need a consult about statistical analysis of a data. Experiment was about fishes and there is two factors effecting the results, which...

    Started by Serhat Turkmen‎, 06-20-2011 11:55 AM
    • Replies: 1
    • Views: 3,228
    06-20-2011, 05:03 PM Go to last post
  56. Conformity with linear gradient (LR assumption)

    Conformity with linear gradient for continuous variables I’m still plugging away through learning logistic regression and I’m at the next to...

    Started by trinker‎, 06-20-2011 01:20 PM
    • Replies: 1
    • Views: 2,248
    06-20-2011, 02:21 PM Go to last post
  57. Adjusted Risk Ratios (proc genmod)

    I'm looking at some risk factors associated with infant death comparing different races to a reference group. I calculated crude risk ratios...

    Started by RyanD‎, 06-20-2011 10:54 AM
    • Replies: 2
    • Views: 8,136
    06-20-2011, 11:39 AM Go to last post
  58. Post Data Normalization from different experiments

    Hi , I have a proteomics data-set, there needs to be some sort of scaling or normalization that needs to be done. So the issue is the data matrix...

    Started by ssvictor‎, 06-15-2011 10:33 AM
    • Replies: 2
    • Views: 4,128
    06-19-2011, 11:01 AM Go to last post
  59. Encorporating species' detection probability into a logistic regression

    Hello statistics peoples, I'm not sure if this is the right forum so please do point me in the right direction if not. I'm looking at using...

    Started by tiggerkate‎, 06-18-2011 10:49 AM
    • Replies: 0
    • Views: 1,804
    06-18-2011, 10:49 AM Go to last post
  60. Survival analysis for 2 different imaging modalities on same patient

    Dear Friends I am working on a project on pediatric cancer. The details are given below. 1. 34 patients underwent PET scan and CT scan at 2...

    Started by venkat‎, 06-11-2011 12:20 AM
    • Replies: 1
    • Views: 1,911
    06-17-2011, 03:23 PM Go to last post

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