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Forum: Biostatistics

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

  1. How to compare only a part of survival vurves?

    My hair got gray now... I have three groups, 3 survival curves ploted, subjects in group 1 & 2 stay around twice as long as in group 3, since the...

    Started by pjaca‎, 06-22-2010 01:23 PM
    • Replies: 6
    • Views: 3,206
    12-01-2010, 04:05 AM Go to last post
  2. Easy question - help asap please?

    I have a sample of 23 white women and 25 African American women. In this sample, ten white women smoke, (13 do not) and 3 black women smoke (22 do...

    Started by stattroubled‎, 12-01-2010 01:03 AM
    • Replies: 1
    • Views: 2,531
    12-01-2010, 01:27 AM Go to last post
  3. Question Calculation for Relative Risk for Overweight and Obesity

    Please take a look at the following: http://ajph.aphapublications.org/cgi/content-nw/full/94/9/1574/T4 I want to figure out how they calculated...

    Started by soytoy‎, 11-27-2010 02:09 AM
    • Replies: 1
    • Views: 4,379
    11-28-2010, 06:26 PM Go to last post
  4. Qtl anova

    Hi, I posted on this site previously but I think maybe the biostatistics section might be more suitable for my problem. It's a genetic data...

    Started by utterlyconfused‎, 11-26-2010 12:52 PM
    • Replies: 0
    • Views: 2,479
    11-26-2010, 12:52 PM Go to last post
  5. log linear model with zero entries

    Hi, I have a log linear model with 4 variables (3 dichotom and 1 ordinal). Some (let's say 5 of 2*2*2*4=32) entries are zero. These zeros random...

    Started by giordano‎, 11-22-2010 01:08 PM
    • Replies: 9
    • Views: 8,508
    11-25-2010, 04:45 AM Go to last post
  6. How to analyze a data set with < & > values?

    We are working on vernal pool botany. *There are two types of pool, Natural (control) and Constructed (experiment). Within each pool, over 8...

    Started by RwM‎, 11-08-2010 08:14 PM
    • Replies: 3
    • Views: 4,360
    11-24-2010, 02:43 AM Go to last post
  7. Need help as a biostatistics moron! Any help appreciated!

    Hello I am completely clueless in statistics and I need help for a problem... The problem is about two study groups regarding the lesion size at...

    Started by kafandiyev‎, 11-21-2010 05:32 PM
    • Replies: 1
    • Views: 3,752
    11-23-2010, 03:19 AM Go to last post
  8. 2-way ANOVA-like analysis with binomial RVs?

    Hi, I have a biological dataset and I'm trying to see if certain treatments are correlated with significant changes. In each sample, I'm...

    Started by nestor‎, 11-20-2010 10:52 PM
    • Replies: 0
    • Views: 6,050
    11-20-2010, 10:52 PM Go to last post
  9. Sampling Question

    I work in a hospital setting and I had a researcher ask me a question about sampling for a control group. We are looking at infection rates...

    Started by noj‎, 11-19-2010 12:15 PM
    • Replies: 0
    • Views: 2,352
    11-19-2010, 12:15 PM Go to last post
  10. Contingency Table questions

    I have a large data set, n=2556. I have two Types, Natural (n=720), Treatment (n=1836) and 3 levels, "Not Present", >0 & <20, and >20. What...

    Started by RwM‎, 11-15-2010 11:08 PM
    • Replies: 1
    • Views: 5,572
    11-17-2010, 12:14 AM Go to last post
  11. Question Mixed model in clnical trials using SPSS

    Design: 3-arm Randomized controlled trials Group: Treatment 1, Treatment 2, and control Assessment time point: Baseline, End-point, follow-up ...

    Started by jerryno34‎, 11-15-2010 07:51 AM
    • Replies: 0
    • Views: 4,613
    11-15-2010, 07:51 AM Go to last post
  12. Comparing screening rates

    Hi all, I've been out of school for a bit and am now having anxiety over picking the correct analysis method for a proposal I have to write. I...

    Started by Thelovecats‎, 11-13-2010 03:44 PM
    • Replies: 0
    • Views: 2,845
    11-13-2010, 03:44 PM Go to last post
  13. Few Questions about P-Value

    This is my first post and I had a few questions which I feel I need help. I have read a few textbooks and papers but I am not sure hence. 1. From...

    Started by anoopbal‎, 11-08-2010 05:21 PM
    • Replies: 3
    • Views: 5,962
    11-08-2010, 07:29 PM Go to last post
  14. stratified sampled analysis

    Hi, I have a data set obteined by a stratified sampling in a cross sectional study. I want to perform logistic regresion analysis however I am...

    Started by gregoepi‎, 10-15-2010 03:21 AM
    • Replies: 3
    • Views: 2,537
    10-29-2010, 05:07 AM Go to last post
  15. Parasites in stats

    Hi everyone, I am having a bit of trouble in understand the stats that I want to run on an experiment I am doing. Basically I want to do a Chi...

    Started by Bonnie‎, 10-28-2010 01:56 AM
    • Replies: 3
    • Views: 2,968
    10-28-2010, 03:45 PM Go to last post
  16. Help in explaining my data, lung cancer- air pollution

    Hi, i am doing a ecological study of 402 distrcits from accross the UK to se wether Air pollution effects lung cancer mortalilty (measured in SMR) ...

    Started by 98107‎, 10-25-2010 05:48 AM
    • Replies: 2
    • Views: 3,230
    10-25-2010, 11:39 AM Go to last post
  17. Cancer survival analysis

    If a new treatment appears to improve median overall survival in a group of patients, is there any way to determine whether this improvement results...

    Started by Doug‎, 10-19-2010 05:41 PM
    • Replies: 3
    • Views: 2,844
    10-24-2010, 05:55 PM Go to last post
  18. Decision Tree

    A friend of mine asked me to help him with a decision tree . I found an online calculator and some resource material but I am not sure how to plug...

    Started by SadieKhan‎, 10-23-2010 12:45 PM
    • Replies: 0
    • Views: 3,797
    10-23-2010, 12:45 PM Go to last post
  19. analysis of the relationship between particulate air pollution and lung cancer

    Hi, I am currently doing a study on Lung cancer mortality and air pollution my hypothsis is to see if there is a link. i have 6 variables ( i...

    Started by 98107‎, 10-20-2010 11:46 AM
    • Replies: 3
    • Views: 5,083
    10-21-2010, 11:00 AM Go to last post
  20. Constant value in logistic regression

    Hi, My question concerns the constant represents in logistic regression analysis (which can be included/excluded in SPSS). I am trying to...

    Started by arb‎, 10-19-2010 09:55 PM
    • Replies: 3
    • Views: 21,667
    10-20-2010, 01:03 PM Go to last post
  21. standard errors, CIs and logistic regression

    A question from a very amateur epidemiologist I am afraid, and a little long winded. I am wondering how to produce the most valid confidence when...

    Started by mcshaz‎, 10-20-2010 04:04 AM
    • Replies: 0
    • Views: 5,757
    10-20-2010, 04:04 AM Go to last post
  22. Question Help with ANOVA: Please Check my Excel file.

    :wave: Hi every one. I am in dire need of help in statistics of my dissertation. I am a pg student in physiotherapy. My thesis is a...

    Started by physio_amer‎, 10-19-2010 12:20 PM
    • Replies: 1
    • Views: 3,869
    10-19-2010, 12:26 PM Go to last post
  23. Aggregate trend analysis

    Someone I work with said they ran across a paper on a study that contained an analysis which looked at the results of several different outcomes to...

    Started by mostater‎, 10-13-2010 03:35 PM
    • Replies: 0
    • Views: 5,078
    10-13-2010, 03:35 PM Go to last post
  24. Structure Activity Relationships... LogP, LogD and drug activity

    Hi, I am a final year PhD research student and i am assessing novel anti-allergy compounds. I have calculated the LogP (how lipophilic the compounds...

    Started by Woodsor‎, 10-10-2010 07:53 AM
    • Replies: 0
    • Views: 4,158
    10-10-2010, 07:53 AM Go to last post
  25. Determining Sample Size

    Hi all: I'm having a bit of trouble with the following exercise: You are asked to design a prospective cohort study comparing the risk that...

    Started by jamesmartinn‎, 09-30-2010 06:59 PM
    • Replies: 2
    • Views: 5,929
    10-08-2010, 06:18 AM Go to last post
  26. SNP or Microsatellite?

    Hi, My project is to get association between these factors (age, color, gender, and performance) of a particular animal to its genotype. Which...

    Started by mike_electron‎, 09-13-2010 11:06 PM
    • Replies: 1
    • Views: 2,602
    10-08-2010, 06:14 AM Go to last post
  27. How to Calculate the Pairwise LD for the given data?

    Dear all, I have the following data, which is the output from ms hudson software. segsites: 6 positions: 0.1256 0.3122 0.3218 0.4970 0.5951...

    Started by jacki.flo‎, 10-07-2010 07:33 PM
    • Replies: 0
    • Views: 4,309
    10-07-2010, 07:33 PM Go to last post
  28. Comparing means problem

    Hi, I have run an experiment where I am comparing the temperature required to cause a febrile seizure in several different animal models of...

    Started by nicolajohnson0009‎, 10-06-2010 11:02 PM
    • Replies: 0
    • Views: 2,321
    10-06-2010, 11:02 PM Go to last post
  29. Error Margins added?

    Dear all, this is my first post on this forum with a quick and probably very stupid question. Let's say I have value of a control distribution...

    Started by plusorminus‎, 10-04-2010 06:45 AM
    • Replies: 1
    • Views: 3,005
    10-04-2010, 10:24 AM Go to last post
  30. Expected value

    I've used Logistic regression to calculate a risk score for death. I've also calculated the probability of dying based on this score. I want to show...

    Started by quirk‎, 10-01-2010 07:05 AM
    • Replies: 1
    • Views: 3,187
    10-02-2010, 03:00 AM Go to last post
  31. Is my study a case-control or a retrospective cohort study?

    Hi All. I'm dipping my toes into medical research and doing an audit of surgical outcomes. I can't work out whether to describe my study as a...

    Started by bm_mode‎, 12-08-2009 10:46 PM
    • Replies: 2
    • Views: 31,455
    09-30-2010, 07:51 PM Go to last post
  32. Drowning in data

    I'm a GP, and am interested in performing better analysis on patient data. The raw data is around 100mb of data. I am fairly adept by now at...

    Started by gwionrhys‎, 09-02-2010 03:58 PM
    • Replies: 9
    • Views: 4,840
    09-28-2010, 05:05 PM Go to last post
  33. help in data analysis for physiotherapy bachelor thesis

    Hi everyone! I'm new here, write from Italy so may you all accept my apologies for my english... hope to be understood anyway. I am graduating in...

    Started by mattiazambaldi‎, 09-20-2010 01:49 PM
    2 Pages
    1 2
    • Replies: 27
    • Views: 8,880
    09-23-2010, 10:29 PM Go to last post
  34. Cox-regression analysis by using the bootstrap weights

    Hi, I am working on a complex survey data set, and I do not have the following variables: Strata and Clusters( because of the confidentiality). On...

    Started by kor‎, 09-21-2010 12:31 PM
    • Replies: 1
    • Views: 5,419
    09-21-2010, 03:53 PM Go to last post
  35. Analyzing bovine mastitis with mixed model in SPSS

    Hi. Im a PhD student working in bovine mastitis. Im trying to analyze a longitudinal study using SPSS version 15. The study consists of 100...

    Started by luchochaneton‎, 09-21-2010 02:29 PM
    • Replies: 0
    • Views: 3,232
    09-21-2010, 02:29 PM Go to last post
  36. Quasi-Randomized vs. RCT

    If a study puts participants in the intervention group based on first come first serve (i.e. the first 65 participants who signed up got the...

    Started by Giulia‎, 09-19-2010 06:03 PM
    • Replies: 5
    • Views: 25,347
    09-21-2010, 11:54 AM Go to last post
  37. Question Survival tree analysis

    I need to perform a survival tree analysis. I have : - 1 independant variable X (numberic variable) - 1 dependant variable Y (overall survival time...

    Started by amoreau1‎, 09-15-2010 04:19 AM
    • Replies: 1
    • Views: 3,991
    09-15-2010, 10:00 AM Go to last post
  38. Choosing a distribution with GEE methods

    I've just recently been exploring Generalized Estimating Equations for use with my data. I know that QIC values can be used to evaluate which working...

    Started by nathanwands‎, 09-14-2010 01:30 PM
    • Replies: 0
    • Views: 3,339
    09-14-2010, 01:30 PM Go to last post
  39. subtract average values with SEM

    I have values of two groups, each has its own mean and calculated standad error of the mean (SEM): A +-SEM(A) B +-SEM(B) I wouls like to...

    Started by almagor‎, 09-12-2010 03:52 AM
    • Replies: 0
    • Views: 4,562
    09-12-2010, 03:52 AM Go to last post
  40. Does cox proportional hazard model control for type 1 error?

    I am a greenhorn to survival analysis. Just wondering if there are many covariates, the likelihood that one of them is significant should be quite...

    Started by hehe1223‎, 09-11-2010 11:04 PM
    • Replies: 1
    • Views: 2,985
    09-12-2010, 12:10 AM Go to last post
  41. neuronal network analysis - what nethod?

    Dear all, I am analyzing the formation of neuronal networks in wild type and transgenic animals. There is very subtle but clear difference in the...

    Started by chottom‎, 09-10-2010 02:40 AM
    • Replies: 1
    • Views: 2,591
    09-10-2010, 02:31 PM Go to last post
  42. can any body comment on the pros and cons of the research methodology

    A Randomized Add-on Trial of an N-methyl-D-aspartate Antagonist in Treatment-Resistant Bipolar Depression Nancy Diazgranados, MD, MS; Lobna Ibrahim,...

    Started by drmg456‎, 09-07-2010 01:25 PM
    • Replies: 3
    • Views: 3,821
    09-08-2010, 09:46 AM Go to last post
  43. Locking a dataset in a stat program

    I'm hoping one of the brilliant minds here will be able to help me with this. First some background I'm in the Epi / Biostat field and currently...

    Started by Link‎, 09-02-2010 08:40 PM
    • Replies: 4
    • Views: 3,652
    09-03-2010, 08:34 PM Go to last post
  44. Question about R code of survival analysis

    I have some questions about cox ph model based on the following demo data set. Thanks a lot for help! > ovarian futime fustat age resid.ds...

    Started by hehe1223‎, 09-01-2010 08:10 PM
    • Replies: 0
    • Views: 3,615
    09-01-2010, 08:10 PM Go to last post
  45. Thumbs up Composite Scores/Standardising scores for cognitive outcomes

    Hi, I am looking into various methods of combining non-independent cognitive outcome measures on different scales in a clinical trials setting ,...

    Started by JG28‎, 08-31-2010 12:20 AM
    • Replies: 0
    • Views: 6,923
    08-31-2010, 12:20 AM Go to last post
  46. Interpretation of Odds Ratios

    I had a basic query regarding interpretation of Odds Ratio. This particular problem was sent to me by one of my colleagues. The risk factor...

    Started by rsstats‎, 04-18-2010 10:47 AM
    • Replies: 5
    • Views: 8,293
    08-26-2010, 02:13 AM Go to last post
  47. McNemar's test and complex survey data

    Hi everyone, I am trying to run McNemar's test on some weighted survey data. I was wondering what changes I have to make to test (if any) to...

    Started by psychgal‎, 08-23-2010 07:13 PM
    • Replies: 0
    • Views: 4,185
    08-23-2010, 07:13 PM Go to last post
  48. Power Calculation- case cotrol study

    I am doing a case control study consisting of 1000 controls and 2000 cases. If it was estimated that 21 of about 1000 women were exposed to solvents....

    Started by medsonia‎, 08-23-2010 10:45 AM
    • Replies: 1
    • Views: 3,291
    08-23-2010, 12:56 PM Go to last post
  49. question about a concept

    Hey When comparing a diagnositic test (questionnaire) to a reference, let us say for disease and no disease, you could calculate sensitivity and...

    Started by noob‎, 08-21-2010 09:32 PM
    • Replies: 0
    • Views: 2,230
    08-21-2010, 09:32 PM Go to last post
  50. Negative variance - using regression. HELP!

    I'm currently writing up a scientific project and I've come to a complete standstill when calculating the variance. The formula I am using to...

    Started by Rachel‎, 08-20-2010 10:12 AM
    • Replies: 0
    • Views: 2,665
    08-20-2010, 10:12 AM Go to last post
  51. Question confidence interval

    if CI of the odds ratio i got was so wide does it have any meaning? and does it make a difference if it contain 1 e.g (0.08- 12) so my...

    Started by nurul‎, 08-17-2010 01:51 AM
    • Replies: 1
    • Views: 2,535
    08-19-2010, 06:13 PM Go to last post
  52. quick biosci stats question

    Hello all, I have a list of patients with their corresponding diagnosis (type of nerve disease) that they received from their primary care provider....

    Started by NeP_res‎, 08-17-2010 06:25 PM
    • Replies: 1
    • Views: 2,969
    08-19-2010, 06:07 PM Go to last post
  53. Iguana Analysis

    Hello! I am a student currently working on iguana data from an island in the Caribbean close to Cuba (dating 20 years). It is a capture-recapture...

    Started by risorial‎, 08-17-2010 05:27 PM
    • Replies: 2
    • Views: 2,510
    08-19-2010, 12:11 AM Go to last post
  54. odds and expected B

    am doing a cross sectional study, now analysing my data. since my data (the outcome is yes and no) and the independant variables all are catigorical...

    Started by nurul‎, 08-17-2010 12:29 AM
    • Replies: 0
    • Views: 2,587
    08-17-2010, 12:29 AM Go to last post
  55. Strange volcano plot

    Hi all, While doing a Limma analysis to compare two groups with two replicates each I am getting this strange volcano plot. Data is comming form...

    Started by patricia garcia‎, 08-12-2010 05:02 AM
    • Replies: 0
    • Views: 3,802
    08-12-2010, 05:02 AM Go to last post
  56. confidence interval interpretation (diagnostic tests)

    If the 95% confidence interval for a relative risk (RR) or an odds ratio (OR) crosses 1, then this is taken as no evidence of an effect = NO...

    Started by adalpra‎, 08-10-2010 04:53 PM
    • Replies: 2
    • Views: 15,935
    08-10-2010, 08:40 PM Go to last post
  57. Urgent! Please Help!! Thank you!!

    Dear All, Please kindly help me, if i don't get this done by monday, my ass (job) will be on the line! Anyway, the problem is below: i have...

    Started by David Wong‎, 08-06-2010 06:58 AM
    • Replies: 3
    • Views: 3,081
    08-09-2010, 07:38 AM Go to last post
  58. Sensitivity and specificity of a subset of items

    I have a list of 60 stimuli and for each one of them, I have their sensitivity, specificity and ji value for the detection of demented vs....

    Started by bergier‎, 08-08-2010 12:47 PM
    • Replies: 0
    • Views: 2,778
    08-08-2010, 12:47 PM Go to last post
  59. High power, bias or low power, unbiased?

    Assuming we have two estimators and a fixed sample size. One estimator is biased and has high power, the other is unbiased and has low power. Which...

    Started by giordano‎, 08-07-2010 11:00 AM
    • Replies: 5
    • Views: 5,743
    08-08-2010, 11:53 AM Go to last post
  60. Anova

    Hello! I have a problem with data analysis and don't know which method to use. Here is a description of my problem: I have cells that have been...

    Started by iced_eax‎, 07-27-2010 07:56 PM
    • Replies: 0
    • Views: 1,971
    07-27-2010, 07:56 PM Go to last post

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