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Forum: Biostatistics

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

  1. Prevalence rates and prevalence odds ratios

    I need to calculate prevalence rates and prevalence odds ratios for a particular disease, classified as 0/1 in my database. In particular, i have to...

    Started by George76‎, 07-08-2009 07:02 AM
    • Replies: 0
    • Views: 5,344
    07-08-2009, 07:02 AM Go to last post
  2. Calculating sensitivity, specificity, etc.of a diagnostic test

    I would like to calculate the specifity, sensitivity, positive and negative predictive value etc. for a diagnostic test, possibly with a method that...

    Started by George76‎, 07-07-2009 07:56 PM
    • Replies: 1
    • Views: 6,973
    07-08-2009, 02:08 AM Go to last post
  3. [Help] Logistic regression and goodness-of-fit

    Hello. I have a question on "goodness-of-fit" of an ordinal logistic regression run that I did. The results of the ordinal logistic regression...

    Started by davidyu77‎, 07-04-2009 11:00 AM
    • Replies: 0
    • Views: 4,231
    07-04-2009, 11:00 AM Go to last post
  4. likelihood contribution

    I have a set of data include survival time, event (1=death; 0=right censored) and treatment (1=yes; 0=no). how to write the likelihood contribution...

    Started by h1n1‎, 06-14-2009 12:30 AM
    • Replies: 0
    • Views: 3,792
    06-14-2009, 12:30 AM Go to last post
  5. Odds ratios with standardised continuous variables?

    Dear TalkStats, I am working on some logistical regression models currently. I understand the interpretation of Odds Ratios, however a friend of...

    Started by DoingPhD‎, 06-09-2009 10:39 AM
    • Replies: 1
    • Views: 7,406
    06-10-2009, 02:17 AM Go to last post
  6. Survival Analysis

    Has anyone ever done a survival analysis (in medical research) where you first include the treatment variable as the only covariate and then do a...

    Started by CharmSchool‎, 06-01-2009 05:51 PM
    • Replies: 3
    • Views: 4,321
    06-02-2009, 10:08 PM Go to last post
  7. Fisher's exact test

    Hello, I'm trying to calculate odds ratio and CI of odds ratio for my thesis data using 2-sided Fisher's exact test. I'm using SPSS and everything...

    Started by zeta09‎, 05-27-2009 08:24 PM
    • Replies: 0
    • Views: 6,557
    05-27-2009, 08:24 PM Go to last post
  8. Logistic Regression output not matching data

    My research question was looking at what factors would best predict which patients are on twice daily insulin dosing. The outcome of interest,...

    Started by waubain‎, 05-27-2009 01:59 PM
    • Replies: 0
    • Views: 2,411
    05-27-2009, 01:59 PM Go to last post
  9. Difference between Sensitivity and Statistical Power?

    Hi, Could anyone point me towards an explanation of the difference between Sensitivity (as described here:...

    Started by simshef‎, 05-14-2009 06:34 AM
    • Replies: 3
    • Views: 13,550
    05-18-2009, 11:28 AM Go to last post
  10. regression P value and odds ratios

    What does it mean if my P value is significant (.010) but the Odds Ratio is low (.66) Is that even possible? SPSS did the calculation.

    Started by nbellinger‎, 05-14-2009 08:03 AM
    • Replies: 1
    • Views: 3,934
    05-14-2009, 09:01 AM Go to last post
  11. Kaplan-Meier vs Nelson-Aalen

    Hi, Working on survival analysis on a bunch of cows that suffer from a common form of disease. I'm trying to get into an analysis pattern here......

    Started by gihund‎, 04-22-2009 10:49 PM
    • Replies: 0
    • Views: 4,675
    04-22-2009, 10:49 PM Go to last post
  12. help with decided what tests to use

    This study will be a prospective clinical trial to compare the effectiveness of nerve and tendon gliding exercises versus no exercise in a group of...

    Started by chungster‎, 04-16-2009 08:44 PM
    • Replies: 0
    • Views: 1,818
    04-16-2009, 08:44 PM Go to last post
  13. Sample Size Calculation

    Dear All, How to derive a sample size for the below scenario... To establish "EQUIVALENCE" for two groups provided we are given with both the...

    Started by Bala‎, 04-07-2009 05:15 AM
    • Replies: 0
    • Views: 2,648
    04-07-2009, 05:15 AM Go to last post
  14. Calculating life expectancy

    I am doing a research project and I need to calculate the life expectancy of a group of musicians. I have a spreadsheet with 400 people and their...

    Started by Justin‎, 03-15-2009 10:58 AM
    • Replies: 2
    • Views: 3,207
    03-18-2009, 06:15 PM Go to last post
  15. which test should i use?

    Hi, if anybody could help with some Biological statisitics then this would be so great: I'm trying to analyse the significance of some cell culture...

    Started by aharrygeorge‎, 03-12-2009 01:29 PM
    • Replies: 3
    • Views: 2,651
    03-15-2009, 11:59 PM Go to last post
  16. A doubt in the terminology of sample size calculation

    Hi all, While going through a published article of a clinical trial in cervical cancer, I came across this statement under statistical...

    Started by placebo‎, 03-11-2009 03:59 AM
    • Replies: 0
    • Views: 2,224
    03-11-2009, 03:59 AM Go to last post
  17. Post Need some help with a survival analysis

    Good Morning! I'm working on a survival analysis involving transplant data. STATUS - graft status TIME - days until graft rejection GROUP -...

    Started by ceperras‎, 03-02-2009 01:31 PM
    • Replies: 0
    • Views: 2,411
    03-02-2009, 01:31 PM Go to last post
  18. calibration of an existing model

    Hi, I would like to assess fitting of a mortality predicting model with original coefficients in another (validation) study population. The...

    Started by jeweetwel‎, 02-27-2009 04:51 AM
    • Replies: 0
    • Views: 2,351
    02-27-2009, 04:51 AM Go to last post
  19. Quasi-Randomized trial

    Hi there, We are conducting a clinical trial comparing the outcomes of 2 surgical interventions (using 2 different commercial products). Our team...

    Started by feiner‎, 02-20-2009 11:22 PM
    • Replies: 1
    • Views: 9,001
    02-21-2009, 06:17 AM Go to last post
  20. Data Format for Repeated Measures AnoVa/SPAnoVa

    Hi everyone, I am a newcomer to the forum, SPSS and stats in general. Having followed the inbuilt tutorials in SPSS (V15) and using Julie Pallant's...

    Started by Random_Man‎, 02-17-2009 01:30 PM
    • Replies: 5
    • Views: 10,138
    02-20-2009, 05:35 AM Go to last post
  21. Multicollinearity in binary logistic regression

    I have two correlated independent variable and I need to use them both (one as a 'interesting' variable, other one as a control variable). Because of...

    Started by zxc‎, 01-07-2009 04:42 PM
    • Replies: 10
    • Views: 26,883
    01-19-2009, 10:03 PM Go to last post
  22. Adjusted Odds Ratio

    Hi to everybody, does anybody knows how to calculate Adjusted Odds Ratio when I have a Multiple Logistic Regression model? Do you know about...

    Started by Canyon75‎, 12-30-2008 05:34 AM
    • Replies: 1
    • Views: 7,477
    12-30-2008, 05:09 PM Go to last post
  23. Incorporating time series date into before/after intelligence testing? (n00b alert)

    Hello there! A short introduction: My background is pure maths and computer science however I did not take anything past first year statistics at...

    Started by boing‎, 12-28-2008 04:21 AM
    • Replies: 1
    • Views: 2,273
    12-28-2008, 05:14 PM Go to last post
  24. clinical statistics book

    Hi, I'm lokking for a book about clinical statistics like this one : 4thEdition Clinical Epidemiology / The essentials / Fletcher & Fletcher ...

    Started by viwel‎, 12-10-2008 09:01 AM
    • Replies: 1
    • Views: 3,393
    12-18-2008, 08:56 AM Go to last post
  25. Help me

    Dear Sir, My wife is a Post Graduate student of Ophthalmology. We desperately seek your help in the analysis of her desertation work. The objectives...

    Started by drriteshsingh‎, 12-14-2008 11:15 AM
    • Replies: 1
    • Views: 2,093
    12-15-2008, 10:21 PM Go to last post
  26. HIV-Testing in the desert

    Hi, In a lot of popular books about statistics (at least in Germany) there is this example about HIV. Even with a sensitivity of say 99%, the...

    Started by giordano‎, 12-14-2008 11:04 AM
    • Replies: 1
    • Views: 2,944
    12-15-2008, 12:40 PM Go to last post
  27. Random Effects Regression vs. Fixed Effects Regression

    I'm having trouble distinguishing when to use random effects versus fixed effects regression. Any thoughts?

    Started by Veronica‎, 12-09-2008 07:44 PM
    • Replies: 6
    • Views: 35,072
    12-10-2008, 08:19 AM Go to last post
  28. Equal Odds

    I'm trying to figure out how I can use logistic regression to test the hypothesis of equal odds in a 2 x 2 table of counts? Any ideas? I know I have...

    Started by jessicka24‎, 12-07-2008 05:47 PM
    • Replies: 1
    • Views: 2,814
    12-07-2008, 10:20 PM Go to last post
  29. Is it ok to average ranks?

    Dear users, I have a following problem, I have a matrix of results of testing of some chemical substances on a set of various experimental objects....

    Started by gemko‎, 11-26-2008 03:55 PM
    • Replies: 0
    • Views: 2,812
    11-26-2008, 03:55 PM Go to last post
  30. Help decide whether I used the right tests

    Hi, I have been doing some statistical tests which I'm a little bit out of my depth on for work. The person I'm doing them for knows less than me,...

    Started by somnum‎, 11-18-2008 10:48 PM
    • Replies: 2
    • Views: 3,009
    11-19-2008, 05:14 PM Go to last post
  31. One for the pros: conditional logistic regression discrepancy

    Ok here´s the problem. I am using R version 2.8.0 on a Windows XP machine. I am not a statistician. I am trying to perform a conditional...

    Started by pisti‎, 11-04-2008 12:14 PM
    • Replies: 8
    • Views: 7,992
    11-07-2008, 06:49 AM Go to last post
  32. omnibus test

    Hi Is it possible to explain me what's an Omnibus Test ??? I find some definitions on Internet but there is'nt some good concrete example ... ...

    Started by viwel‎, 10-28-2008 09:19 AM
    • Replies: 4
    • Views: 29,175
    10-30-2008, 09:00 AM Go to last post
  33. What do YOU mean by "statistically significant"?

    Here's a question more about communication than statistical methods. I've experienced that the term "statistically significant" is used often by...

    Started by jawon‎, 10-06-2008 06:19 PM
    2 Pages
    1 2
    • Replies: 25
    • Views: 13,120
    10-22-2008, 04:40 PM Go to last post
  34. Help! Data layout and which test?

    Hi, :wave: I have some data on a clinical trial. 2 Independent groups, running in paralell, treatment and placebo(n=50). Biological markers...

    Started by stinker‎, 09-30-2008 10:03 AM
    • Replies: 3
    • Views: 3,261
    10-14-2008, 08:06 AM Go to last post
  35. Logistic regression with continuous variables

    I have levels of eight biochemical markers (continuous variables) and want to determine whether each marker helps to predict the presence or absence...

    Started by rbody‎, 10-06-2008 03:54 PM
    • Replies: 4
    • Views: 11,318
    10-07-2008, 05:26 AM Go to last post
  36. Plotting PPV vs. NPV, why?

    Hi, I was asked to plot PPV vs NPV, and I'm not sure what such a plot does in general. Is it similar to an ROC curve (sensitivity vs....

    Started by pufftissue‎, 10-01-2008 12:51 PM
    • Replies: 0
    • Views: 4,388
    10-01-2008, 12:51 PM Go to last post
  37. More Repeated Measures Problems!

    Hi guys, I have a similar question to johnstephenbyrne. I am analysing the results of a clinical trial. I have measured the levels of a cytokine...

    Started by timric‎, 09-08-2008 07:08 PM
    • Replies: 2
    • Views: 3,859
    09-17-2008, 04:22 PM Go to last post
  38. Wink biostatistical problem--birds and patch size

    I have an interesting statistical problem I'm having trouble solving...here's the story: I repeatedly sampled birds along 100m-long transects in...

    Started by birdman‎, 09-15-2008 11:57 AM
    • Replies: 5
    • Views: 3,319
    09-17-2008, 07:40 AM Go to last post
  39. Question Calculating sensitivity and specificity of a *battery* of tests

    Hello everyone! I need to calculate the specificity, sensitivity, positive and negative predictive values of a battery of neuropsycholocial...

    Started by bergier‎, 07-09-2008 03:49 PM
    • Replies: 3
    • Views: 6,630
    08-30-2008, 05:52 AM Go to last post
  40. diagnostic testing

    Medical Testing When evaluating a diagnostic test, one typical constructs a 2 x 2 table and calculates the specificity and sensitivity (true and...

    Started by denmanbw‎, 01-22-2008 01:01 PM
    • Replies: 1
    • Views: 2,944
    08-30-2008, 05:45 AM Go to last post
  41. Clinical Study and Biostatistics

    Hy everyone, I have measured a biological parameter in a cohort of 20 patients before they start a therapy (baseline) and then every 2 months for a...

    Started by mnasi‎, 08-21-2008 08:42 AM
    • Replies: 2
    • Views: 2,733
    08-26-2008, 05:19 AM Go to last post
  42. Repeated measures with censoring

    I am conducting an experiment to test spin times of tops. I have 5 aluminum tops and 5 wooden tops. I spin each top 3 times with a maximum spin...

    Started by wayne‎, 08-04-2008 07:41 PM
    • Replies: 2
    • Views: 2,658
    08-05-2008, 12:23 PM Go to last post
  43. likelihood ratio for censored data

    hi, I'm working on multiply censored data. In order to check which is the law my data follow(weib vs exp), i need to do a test. For the moment,...

    Started by edwin_35‎, 07-25-2008 04:08 PM
    • Replies: 1
    • Views: 3,864
    07-27-2008, 09:35 AM Go to last post
  44. stats for following nominal variables over time??

    Hi all, I'm trying to find a method of examining the patterns in symptoms over time. These are only nominal categories. Each patient has...

    Started by hmwestern‎, 07-17-2008 03:39 PM
    • Replies: 1
    • Views: 2,664
    07-17-2008, 03:54 PM Go to last post
  45. Not sure which test to use...

    Hi everyone, thanks for reading. I'll try and make this quick, so that hopefully once I know which test I should use I can go and have a go rather...

    Started by Stuck‎, 06-08-2008 08:27 AM
    • Replies: 0
    • Views: 2,166
    06-08-2008, 08:27 AM Go to last post
  46. unsure about response

    For the data set below, I want to fit a model for log seizure rate, including the main effect of treat and time (as categorical variable with 5...

    Started by dwen‎, 05-30-2008 09:30 PM
    • Replies: 1
    • Views: 3,234
    06-01-2008, 05:04 AM Go to last post
  47. Question I Need help with median and variance...

    ::wave: hi every1 .. i need help with a biostatistics problem... well it was in spanish so i dont know if i made a good job translating but they are...

    Started by Js1&OnLY‎, 04-22-2008 06:17 PM
    • Replies: 1
    • Views: 2,445
    04-22-2008, 06:23 PM Go to last post
  48. Odds ratio

    I am studying risk for cardiovascular disease depending on two different biomarkers. The study -design is a case-control study and I have...

    Started by JonasPerssonSthlm‎, 04-14-2008 05:05 AM
    • Replies: 0
    • Views: 3,144
    04-14-2008, 05:05 AM Go to last post
  49. Which test to use for correlation between groups using ordinal values?

    I am trying to test a hypothesis that different decision traps are caused by the same common cause. In the complete picture there are abt 30 decision...

    Started by rlammers‎, 04-01-2008 07:41 AM
    • Replies: 0
    • Views: 3,334
    04-01-2008, 07:41 AM Go to last post
  50. logistic regression

    in logistic regression what does an exp 1 means? that the odds increase or that they remain the same?

    Started by casiva‎, 03-12-2008 10:55 AM
    • Replies: 1
    • Views: 3,734
    03-12-2008, 12:14 PM Go to last post
  51. Odds ratios and regression

    It's my understanding that odds ratios derived from (multiple) logistic regression is based upon a single unit increase of your variables. If the...

    Started by BenW‎, 02-28-2008 07:48 AM
    • Replies: 0
    • Views: 2,703
    02-28-2008, 07:48 AM Go to last post
  52. Relative Impact of Predictors with a Binary Logistic Regress

    Hi, I'm trying to find a means to interpret the odds ratios resulting from a binary logistic regression. I have a binary response variable and...

    Started by Crystal‎, 02-19-2008 07:59 PM
    • Replies: 0
    • Views: 2,370
    02-19-2008, 07:59 PM Go to last post
  53. hello all, please help me choose the statistical test for my research

    I am looking at a database and would need help on what statistical test to use for my research project. There are four groups (for example cars...

    Started by mdme‎, 01-03-2008 12:07 PM
    • Replies: 2
    • Views: 3,994
    01-12-2008, 05:57 AM Go to last post
  54. Angry Null Hypothesis for OR

    I got this question: "In the background for this study, the authors mentioned that “Data from the Sleep Heart Health Study (Baldwin et al., 2001)...

    Started by abrenner‎, 11-28-2007 02:55 PM
    • Replies: 1
    • Views: 3,508
    11-28-2007, 07:23 PM Go to last post
  55. EBM Stats

    Hi everyone - my first post! Was wondering if anyone could help me. I am doing a project on the outcomes of a particular type of eye surgery...

    Started by 7up‎, 11-13-2007 07:30 AM
    • Replies: 1
    • Views: 2,614
    11-25-2007, 12:23 PM Go to last post
  56. Writing a Life Regression Model with Minitab Output

    Alrighty, I feel incredibly dumb here so please bear with me. :( I have the following output from minitab from a life regression. Now, what I want...

    Started by IronMan‎, 11-08-2007 05:20 PM
    • Replies: 1
    • Views: 3,723
    11-15-2007, 10:48 AM Go to last post
  57. Question I need so much help in statistics....I have alot of questions, please help me.

    Hi there, Im taking a statistics class online right now because Im going for a degree in Bio technology. When I comes to math I just get so confused...

    Started by megank‎, 11-11-2007 01:14 PM
    • Replies: 1
    • Views: 8,040
    11-12-2007, 11:18 AM Go to last post
  58. LD50 power analysis

    Hello all, I come from a biology background, and I wanted to ask a question. We have a value of LD50 (lethal dose), which is the dose at which 50%...

    Started by Shiranai‎, 11-08-2007 05:56 PM
    • Replies: 2
    • Views: 4,273
    11-09-2007, 02:22 PM Go to last post
  59. who can provide good forum about clinical trial data management and biostatistics?

    thank you very much!!!多谢大家啦!!!

    Started by orientaldream‎, 10-29-2007 11:08 PM
    • Replies: 0
    • Views: 5,607
    10-29-2007, 11:08 PM Go to last post
  60. Question Probit Analysis on Limited Data

    My problem is how to address data on mortality rates of spiders exposed to three temperatures. I have done probit to analyse similar data with...

    Started by kencil‎, 07-20-2007 10:29 AM
    • Replies: 4
    • Views: 3,884
    10-23-2007, 07:11 AM Go to last post

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