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Forum: Biostatistics

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

  1. Into which components put the covariates?

    Hi, I would like to fit to my data Gompertz-Makeham (G-M) mortality model with covariates (sex and particular disease - both are dichotomous...

    Started by butasbutauskas‎, 03-19-2011 05:32 PM
    • Replies: 0
    • Views: 2,463
    03-19-2011, 05:32 PM Go to last post
  2. interpretation ROC curves

    Hi Papers evaluating diagnostic tests for performance use ROC curves. This evaluates the sensitivity and specificity of a test over different...

    Started by noob‎, 03-03-2011 05:55 PM
    • Replies: 5
    • Views: 7,433
    03-17-2011, 07:11 PM Go to last post
  3. Question Question: how to account for spatial variation?

    Hello, This is my first time posting to this forum, I hope this question wasn't recently addressed! I have a small dataset of samples with...

    Started by lstanish12‎, 03-10-2011 05:11 PM
    • Replies: 0
    • Views: 2,415
    03-10-2011, 05:11 PM Go to last post
  4. Exclamation Question about logistics regression.

    I have question about logistics regression. I have 3 year survey data 2005,2006,2007. Risk behavior, let say r1 r2 r3 r4 …etc and outcome (which is...

    Started by dinsya‎, 03-09-2011 08:38 AM
    • Replies: 2
    • Views: 3,646
    03-10-2011, 02:21 AM Go to last post
  5. What p value to use in Repeated measures

    Hi there I am running a very simple repeated measured model with one group of subjects with samples taken every hour for six hours. I am using...

    Started by Maxine‎, 03-01-2011 12:02 AM
    • Replies: 1
    • Views: 3,934
    03-07-2011, 09:45 AM Go to last post
  6. Correlation but not significant difference

    I have to critique a paper for one of my classes but I am having issues when it comes down to the stats. The paper is on the connection between...

    Started by washburnk‎, 03-05-2011 07:52 PM
    • Replies: 1
    • Views: 9,395
    03-07-2011, 09:26 AM Go to last post
  7. Using Age as Time Scale

    I am generally a SAS user, I had a general question concerning how to fit survival models using age as the time scale within R. Would this fit...

    Started by kcf5005‎, 03-06-2011 01:08 PM
    age as time scale, epidemiology, survival analysis
    • Replies: 0
    • Views: 3,005
    03-06-2011, 01:08 PM Go to last post
  8. Masters thesis feedback from senior members/contributors

    Hi fellow members, The time has come for me to start work on my master's thesis in hopes that I'll be able to publish it in a peer reviewed...

    Started by Link‎, 11-02-2010 05:58 PM
    • Replies: 10
    • Views: 5,991
    03-04-2011, 06:51 PM Go to last post
  9. HELP! Stats method for comparing curves?

    Hello all, I was hoping you guys might be able to assist me, I'm in the middle of writing a biology honors thesis and I'm trying to compare the...

    Started by WestCape‎, 03-03-2011 12:50 AM
    graphs, nominal variable, stats
    • Replies: 1
    • Views: 3,647
    03-03-2011, 06:16 PM Go to last post
  10. Post Help for Case-Control Study Statistical Analysis

    Hi All, I'm new to this forum and this is my first post, so please be patient with me! :) I'm processing some data from a case-control study on...

    Started by Jashin_212‎, 02-21-2011 10:00 AM
    • Replies: 2
    • Views: 7,643
    03-02-2011, 09:45 PM Go to last post
  11. What statistical test should I use?

    hello guys, I am doing some statistics and I am a little confused on which test is the most appropriate to calculate the P value. I have a...

    Started by scerab‎, 01-28-2011 12:13 PM
    2 Pages
    1 2
    • Replies: 25
    • Views: 14,056
    03-01-2011, 04:43 PM Go to last post
  12. Covariance structure question for mixed model repeated measures ANCOVA

    I'm working on a mixed model repeated measures ANCOVA and am working on identifying the covariance structure for my model. I am interested in...

    Started by KLSmithBio‎, 02-28-2011 11:09 PM
    ancova, covariance structure, repeated measures
    • Replies: 0
    • Views: 3,663
    02-28-2011, 11:09 PM Go to last post
  13. How to compare bed time using SPSS

    I am going to compare the bed time between 2 groups. Some of them go to bed before midnight (e.g. 22:00) and some of them after midnight (e.g....

    Started by jerryno34‎, 02-27-2011 11:36 PM
    • Replies: 2
    • Views: 8,922
    02-28-2011, 08:20 PM Go to last post
  14. easy question/ sensitivity

    Hi So the sensitivity of a test is equal to true positives/(true positives + false negatives). Now what if I have a test I want to evaluate....

    Started by noob‎, 02-28-2011 06:39 PM
    • Replies: 1
    • Views: 2,393
    02-28-2011, 07:06 PM Go to last post
  15. Necessary to use twofactorial ANOVA when to compare two stratified groups?

    I have a situation were we are going to compare to treatments. We will have one treatmentgroup and one controlgroup. The treatment is a new kind...

    Started by kabooze‎, 02-28-2011 02:10 AM
    • Replies: 1
    • Views: 3,361
    02-28-2011, 03:16 AM Go to last post
  16. sample size

    :confused: :confused: Hi...am a medical doctor and new to academic research .. however i have some knowlege on methodology and basic statistics. ...

    Started by Besucher‎, 01-18-2011 05:25 AM
    • Replies: 1
    • Views: 2,254
    02-27-2011, 08:58 PM Go to last post
  17. Question Source of Pseudoreplication in data?

    Hi, As part of my dissertation, I'm going to be doing an Anova, comparing the "dead zone" diameters on plates of microbial growth with little paper...

    Started by Axolotl9250‎, 02-26-2011 11:07 AM
    anova, pseudoreplication
    • Replies: 0
    • Views: 2,669
    02-26-2011, 11:07 AM Go to last post
  18. How to analysis impact vs control data

    Can you please help? I'm trying to assess if the treatment applied to Impact sites has altered the soil properties as observed in the control...

    Started by Soilguru‎, 02-24-2011 05:18 PM
    • Replies: 3
    • Views: 4,416
    02-25-2011, 05:09 PM Go to last post
  19. Time Varying Covariates Cox Regression

    Hello! A quick run down of my situation. I'm fitting a multivariable cox proportional hazards model with the following specifications: Patients...

    Started by jamesmartinn‎, 02-22-2011 05:21 AM
    • Replies: 1
    • Views: 4,006
    02-22-2011, 10:31 AM Go to last post
  20. Any software for Fleiss' kappa?

    I would like to perform a Fleiss' kappa test, which, however, is not available in SPSS. Are there any online calculators or software packages...

    Started by jerryno34‎, 02-17-2011 10:45 PM
    • Replies: 3
    • Views: 5,905
    02-18-2011, 02:24 AM Go to last post
  21. Results of two way ANOVA interaction=empty cells: Programming or stats error?

    Wow, this is a fantastic site! :) This is my first time doing ANOVA. I have a table of mean ratios ("x") calculated from a large data set (n~2...

    Started by dididph‎, 02-17-2011 02:23 AM
    • Replies: 2
    • Views: 8,290
    02-17-2011, 03:09 AM Go to last post
  22. Arrow Interpreting Cox proportional hazards regression p values

    Hi guys, I have been testing the hypothesis for difference of survival between four different classes by using coxph function of survival package...

    Started by jacks‎, 02-16-2011 02:39 AM
    • Replies: 2
    • Views: 10,547
    02-16-2011, 05:35 AM Go to last post
  23. help- comparison of 2 groupes of categorical data‏

    Dear all, I may need your suggestion for a statistical question. Now I have 2 groupes of data, I wanna see if there are differences in the...

    Started by lilylily‎, 02-10-2011 10:07 AM
    • Replies: 6
    • Views: 235,621
    02-15-2011, 10:28 AM Go to last post
  24. Trend test

    I am working on a data set with two variables (male and female). Each of these variables corresponds to the # of clients seen in a month. I would...

    Started by Kelvin‎, 02-15-2011 06:29 AM
    • Replies: 0
    • Views: 3,113
    02-15-2011, 06:29 AM Go to last post
  25. How do I compare 2 sets of measurements taken at different times?

    Dear All I'm not sure how to compare the following data. I am doing a retrospective study to see whether treating surface eye disease can...

    Started by SiBorg‎, 02-14-2011 06:24 AM
    • Replies: 0
    • Views: 3,133
    02-14-2011, 06:24 AM Go to last post
  26. help on experimental design and statistics

    I'd need some advice about a statistical issue pointed out by a reviewer and that I have not really understood. The experiment was carried out in...

    Started by trimz79‎, 02-14-2011 06:02 AM
    • Replies: 0
    • Views: 2,864
    02-14-2011, 06:02 AM Go to last post
  27. Trends incidence

    Hello, I have to modelize standardized incidence rates with SAS software. It seems that I will use poisson regression model and don't find how to...

    Started by Lola lv‎, 01-10-2011 01:22 PM
    • Replies: 3
    • Views: 5,172
    02-10-2011, 12:58 PM Go to last post
  28. 2 x 2 ANOVA vs. Paired t-test

    I'm trying to figure out which is more appropriate for a trial. I have two groups in a double-blinded, randomized, placebo-controlled trial. We are...

    Started by ricktan‎, 02-09-2011 12:37 PM
    • Replies: 0
    • Views: 4,314
    02-09-2011, 12:37 PM Go to last post
  29. stats for sex/age ratios

    Hi. I am doing a paper on trapping ratios of mammals. Looking at the total number of male vs female initial captures, recaptures (2nd time) and...

    Started by luna‎, 02-08-2011 05:39 PM
    • Replies: 0
    • Views: 3,396
    02-08-2011, 05:39 PM Go to last post
  30. Epidemiology

    How do i calculate actual antibody prevalence in the population of persons whose blood samples will undergo a second test? Assume the population is...

    Started by jshammah‎, 02-07-2011 09:39 AM
    • Replies: 0
    • Views: 3,778
    02-07-2011, 09:39 AM Go to last post
  31. Repeated Measures ANOVA and Inter-rater reliability

    I need some step-by-step help with setting up a repeated measures ANOVA for the purpose of running an inter-rater reliability ICC for 2 raters,...

    Started by timothyspeicher‎, 02-05-2011 11:08 AM
    • Replies: 0
    • Views: 6,815
    02-05-2011, 11:08 AM Go to last post
  32. Hidden State Modeling

    The disease state is continuously changing in patients and I want to be able to predict this change (slope) ahead of time using 3 variables measured...

    Started by psurana‎, 02-04-2011 07:06 AM
    • Replies: 0
    • Views: 3,023
    02-04-2011, 07:06 AM Go to last post
  33. Confused

    Hi! I'm taking a class in applied categorical data analyses and I'm having a bit of trouble getting my head around what I think is a central part...

    Started by jamesmartinn‎, 01-29-2010 10:49 PM
    • Replies: 4
    • Views: 3,613
    01-30-2011, 04:37 PM Go to last post
  34. Need help with statistical analysis of an experiment

    I'm having a hard time to preform statistical analysis on an experiment of mine. So I was hoping maybe someone here could give me some advice. I...

    Started by Doczago‎, 01-19-2011 07:02 AM
    • Replies: 1
    • Views: 3,062
    01-29-2011, 05:37 PM Go to last post
  35. Model selection on Orthogonal data

    Hi, I have a question whether or not it is really necessary to do model selection if one has orthogonal data and no correlation between...

    Started by kalle2‎, 01-17-2011 05:49 PM
    • Replies: 1
    • Views: 4,159
    01-25-2011, 06:16 PM Go to last post
  36. comparing two graphs using area under the curve

    I have a graph which the x axis is hour of the days for 3 consecutive days and the y axis is the time rat mothers spent with their pups for every...

    Started by aridan.bi‎, 12-28-2010 03:40 AM
    • Replies: 2
    • Views: 7,278
    01-25-2011, 02:06 AM Go to last post
  37. ANOVA exam Q help please

    Hi I have an exam coming up and need some help with a sample ANOVA question. I can post the question if needs be but mainly i'm looking for a...

    Started by utterlyconfused‎, 01-21-2011 02:39 PM
    • Replies: 0
    • Views: 2,752
    01-21-2011, 02:39 PM Go to last post
  38. Confidence intervals for percentages

    Hi there If i have a larger than 2x2 contingency table, does any one know how to calculate confidence intervals for the cell percentages? Say for...

    Started by scarper‎, 01-18-2011 11:32 AM
    • Replies: 0
    • Views: 2,534
    01-18-2011, 11:32 AM Go to last post
  39. design for three treatments

    Hi all, I'm debating about the most appropriate design for a study with three treatments. Parallel is an option and using a conservative "divide...

    Started by DaveC‎, 01-16-2011 04:23 PM
    • Replies: 0
    • Views: 2,362
    01-16-2011, 04:23 PM Go to last post
  40. Redundancy Analysis in R

    I do hope this question is not too specific, but reading previous posts I have been very impressed with the knowledge of the responders, and the...

    Started by jasper1233‎, 01-13-2011 12:44 PM
    redundancy analysis, vegan
    • Replies: 0
    • Views: 6,977
    01-13-2011, 12:44 PM Go to last post
  41. need help to solve this!!! ASAP

    Problem: Investigators explored the association of type of contraceptive use history on intelligence of subsequent offspring using the Wechsler...

    Started by destiny‎, 01-11-2011 10:26 AM
    • Replies: 0
    • Views: 2,260
    01-11-2011, 10:26 AM Go to last post
  42. Two test results from one population -> OK to use Chi-Square test of independence?

    I have 195 patients from whom I have two test results: test1 and test2. The results were obtained by measuring immunoglobulin G (IgG) levels in...

    Started by Compton‎, 12-31-2010 12:22 PM
    • Replies: 3
    • Views: 6,240
    01-08-2011, 01:12 AM Go to last post
  43. Standard deviation mean estimate for time series with autocorrelation

    Hi! I'm facing a problem in estimating the standard deviation of mean estimate in a time series with autocorrelation. My data set is daily...

    Started by santtila‎, 12-28-2010 10:09 PM
    • Replies: 1
    • Views: 9,653
    01-06-2011, 12:27 PM Go to last post
  44. best test to use

    hi i recently did an experiment to find out whether a population of 160 jellyfish were all clones of one jellyfish or not. To find this out a pair of...

    Started by kbentley_1‎, 01-06-2011 06:42 AM
    • Replies: 0
    • Views: 1,953
    01-06-2011, 06:42 AM Go to last post
  45. Normal distribution...

    Hello! I'm doing probability exercises and I found one that relates the normal distribution with sensitivity and specificity, and I do not know...

    Started by Fidias‎, 01-03-2011 02:33 PM
    • Replies: 0
    • Views: 2,164
    01-03-2011, 02:33 PM Go to last post
  46. Study Design - McNemar's test appropriate?

    Hi, I have a question regarding the study which I am currently planning. I have to add that I am a physician and not a statistician, and that I am...

    Started by ebm‎, 12-31-2010 09:35 AM
    • Replies: 4
    • Views: 5,807
    01-02-2011, 12:24 PM Go to last post
  47. Exclamation test with proportions

    hi :wave: i have chosen a consecutive sample for research. i want to apply hypothesis test for difference in proportions by dividing the data into...

    Started by aish‎, 12-21-2010 03:45 AM
    • Replies: 5
    • Views: 3,391
    12-25-2010, 02:28 PM Go to last post
  48. none of the variables were significant

    Hey everyone, I have a set of data (n=3000, 48% males and 52% females) from a cross sectional study. I got 20 explanatory variables (let's say...

    Started by Gee Smarty‎, 12-24-2010 04:28 AM
    • Replies: 3
    • Views: 3,429
    12-25-2010, 04:34 AM Go to last post
  49. General two-way ANOVA questions

    Hi, I have the following factors in my data: pretreatment (yes or no), drug_dose (1, 2, 3, 4) and neurochemical levels (dependent variable). ...

    Started by sfishe‎, 12-20-2010 06:10 PM
    • Replies: 4
    • Views: 10,146
    12-21-2010, 03:16 AM Go to last post
  50. Interpreting an interaction matrix

    Greetings, fellow statisticians! As final assignment of my statistics class (CRUCIAL to passing), I have to analyse data presented to me in form...

    Started by c-met‎, 12-16-2010 09:40 PM
    • Replies: 0
    • Views: 2,348
    12-16-2010, 09:40 PM Go to last post
  51. What to use on SPSS

    I am doing a project with data from a cohort of babies born with a low birthweight. I have done basic descriptive stats, but I don't know which...

    Started by stattroubled‎, 11-26-2010 07:39 PM
    • Replies: 4
    • Views: 2,996
    12-14-2010, 03:15 AM Go to last post
  52. Subpopulation?

    Hey guys would you consider two different graduating classes to be a subpopulation? For instance highschool grad class of 2000 and highschool grad...

    Started by Pineapple‎, 12-10-2010 12:01 AM
    • Replies: 1
    • Views: 2,428
    12-10-2010, 09:57 PM Go to last post
  53. [SPSS] ANCOVA (on 2 treatments) or independant t-test on change (post - pre value)

    Hi guys, I'm working on my thesis and recently handed in my research proposal. A quick summary of my research is: 2 treatments groups (exercise...

    Started by BBD‎, 12-06-2010 01:18 PM
    • Replies: 1
    • Views: 7,415
    12-08-2010, 09:23 AM Go to last post
  54. How to interpret This Plot - Please Help

    Hello, Thank you for reading this post. Can someone please tell me why some of the censored points in this survival plot are falling under the...

    Started by khaaver‎, 12-08-2010 05:33 AM
    • Replies: 0
    • Views: 2,503
    12-08-2010, 05:33 AM Go to last post
  55. Hi Can you solve this problem

    Moderators please remove this thread. Thank you.

    Started by biostatstudent‎, 12-08-2010 02:39 AM
    • Replies: 0
    • Views: 2,734
    12-08-2010, 02:39 AM Go to last post
  56. ANOVA help please

    Hi All, I have an assignment on analysis of variance and I need help please. I have a model (Yi(j)k = μ Qi + g(Q)j(i) + εi(j)k) and i need to...

    Started by unterglayben‎, 12-07-2010 06:25 PM
    • Replies: 0
    • Views: 1,693
    12-07-2010, 06:25 PM Go to last post
  57. GLM poisson

    I fit a GLM poisson model and the residual deviance is 64 on 30 degrees of freedom. Does this mean it's poorly fit compared to the...

    Started by zzzc‎, 12-06-2010 12:18 AM
    • Replies: 0
    • Views: 2,891
    12-06-2010, 12:18 AM Go to last post
  58. Measuring strength of an association

    Hey guys, I'm a little stuck I'm trying to analyze the strength of an association between cancer remission (yes or no) versus number of pets (0-5). I...

    Started by Pineapple‎, 12-05-2010 08:20 PM
    • Replies: 11
    • Views: 7,298
    12-05-2010, 11:40 PM Go to last post
  59. Epidemiology Cliches Question

    Greetings all, since epidemiology ecological analysis and hierarchical modelling is not my main field, I would like to ask a few (probably stupid)...

    Started by Navaak‎, 12-02-2010 05:36 AM
    • Replies: 2
    • Views: 3,661
    12-04-2010, 10:51 AM Go to last post
  60. Power Analysis: MANOVA for repeated measures design?

    I recently collected some pilot data for a project using a repeated measures design. One group of 6 subjects, two within-subject factors, each with...

    Started by GaetanoL‎, 12-03-2010 06:35 PM
    • Replies: 0
    • Views: 4,830
    12-03-2010, 06:35 PM Go to last post

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