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Forum: Biostatistics

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

  1. Wink standardizing count data over different time periods?

    Hi all, I am analyzing the number of juveniles female insects produced on a series of host plants, with the females themselves being reared on...

    Started by BWGIA‎, 01-25-2012 12:45 AM
    • Replies: 0
    • Views: 2,113
    01-25-2012, 12:45 AM Go to last post
  2. Statistical significance of biological ratios.

    I have a data set that i'm trying to analyse at the moment, which is comprised of plankton species and abundance data. There are 4 locations, and...

    Started by _Alex_‎, 01-24-2012 06:56 AM
    • Replies: 0
    • Views: 3,328
    01-24-2012, 06:56 AM Go to last post
  3. Adverse drug reaction; multiple drugs, possible event(s) per patient. What analysis?

    Hello everyone, I am currently looking for the right method to compare the incidences of a given adverse drug reaction (infection) after the...

    Started by maksler‎, 01-24-2012 04:25 AM
    adverse drug reaction, design, observational study
    • Replies: 0
    • Views: 2,283
    01-24-2012, 04:25 AM Go to last post
  4. Replace ANOVA interaction term pvalue with ROC AUC - how?

    Hi all, First post here, so please feel free to let me know I'm asking in the wrong place or doing something similarly horrible. That said... ...

    Started by Qroid‎, 01-20-2012 05:10 PM
    • Replies: 1
    • Views: 2,711
    01-22-2012, 02:05 PM Go to last post
  5. Randomization for animal trial

    I am planning a study with animals. I need to randomize them before the start of the trial based on glucose levels, so that each group starts with...

    Started by glucosecat‎, 01-20-2012 06:53 PM
    • Replies: 0
    • Views: 2,997
    01-20-2012, 06:53 PM Go to last post
  6. Sample Size calculations with sub-groups

    I am in a situation wher we need to recruit 1600 people with a particular condition (calculated so that we can detect a 5% change following...

    Started by gopher‎, 01-20-2012 05:50 AM
    over-sampling, sample size, stratified sampling
    • Replies: 0
    • Views: 2,865
    01-20-2012, 05:50 AM Go to last post
  7. Quality adjusted survival analysis

    One question, is it possible to have an increased quality adjusted survival during a period of time? I ask that because I saw a paper published in a...

    Started by motaveiga‎, 01-16-2012 05:27 AM
    • Replies: 5
    • Views: 3,111
    01-19-2012, 08:04 PM Go to last post
  8. cross over trial

    Good day I would like some imput on what whould be the most appropriate test to do in this case: I have a cross over trial in which two...

    Started by Brand‎, 01-18-2012 05:49 PM
    chi square, cross over, fisher exact test, gart's test
    • Replies: 1
    • Views: 1,601
    01-19-2012, 01:08 AM Go to last post
  9. Which kind of a design is it ?

    Hello guys, I have a theoretical question. I have an experiment, in which we try to see if a new machine can detect a disease. In order to check...

    Started by NN_STAT‎, 01-12-2012 04:55 AM
    • Replies: 5
    • Views: 2,473
    01-17-2012, 03:36 PM Go to last post
  10. Generalized estimating equations

    I am planning a randomized controlled cluster trial and was hoping to get some advice on using GEE's. My question is can GEE's have a different...

    Started by viostorm‎, 01-09-2012 02:14 PM
    • Replies: 2
    • Views: 1,935
    01-17-2012, 12:38 PM Go to last post
  11. Concordance index in survival analysis (cox regression) adjusted for competing risk

    Hello everybody! First of all this is truely a wonderful place for discussion about statistics. I have been looking here from time to time and I...

    Started by Sirikon‎, 01-11-2012 09:33 AM
    competing risks, concordance index
    • Replies: 3
    • Views: 10,936
    01-17-2012, 12:37 PM Go to last post
  12. interaction in logistic regression

    Hi All, looked through some posts relevant to interaction terms in logistic regression, couldn't find the extract answer to my question, thus post...

    Started by Guan‎, 01-06-2012 01:33 PM
    • Replies: 6
    • Views: 5,062
    01-13-2012, 05:52 AM Go to last post
  13. Bayes Theorem / Contingency Tables

    In this example, I will walk you through the classic Bayes Theorem question concerning diagnostic tests. Rather than memorize a bunch of formulas...

    Started by JohnM‎, 11-09-2005 11:40 AM
    • Replies: 8
    • Views: 17,904
    01-09-2012, 09:01 AM Go to last post
  14. Determining significant (or otherwise) difference between 2 rates of change

    Dear Users, I am trying to determine the statistical significant difference (or otherwise) between 2 series of data and am unsure how to proceed....

    Started by Axial‎, 01-01-2012 02:56 PM
    rate, rate of change, significant difference
    • Replies: 7
    • Views: 21,571
    01-09-2012, 02:21 AM Go to last post
  15. Lightbulb Quantifying trends and patterns, which test to use?

    Attached is an image of some graphs showing the relationship between a factor which varies year on year, compared to various other factors. With many...

    Started by andyw‎, 01-08-2012 01:51 PM
    • Replies: 3
    • Views: 2,854
    01-08-2012, 04:00 PM Go to last post
  16. Post-hoc multiple comparisons are significant but interaction term is not signicant

    I could use some help with interpreting the results of a statistical analysis conducted using generalized linear mixed models fitted with the GLIMMIX...

    Started by statmanjohn‎, 07-30-2011 04:36 PM
    • Replies: 1
    • Views: 3,204
    01-06-2012, 03:59 PM Go to last post
  17. Confounders Control

    Hello, I have a small theoretical question. Is it correct to use multivariate linear regression to control for confounders ? for example, if I...

    Started by NN_STAT‎, 12-28-2011 12:53 AM
    • Replies: 1
    • Views: 2,194
    01-05-2012, 08:44 AM Go to last post
  18. Sample Size for Chi Square test

    Hello, I need to calculate a minimum sample size for the chi square test. I have two groups, sick and healthy patients, and I have a new test...

    Started by NN_STAT‎, 01-04-2012 02:38 AM
    • Replies: 7
    • Views: 37,525
    01-05-2012, 06:49 AM Go to last post
  19. Measure of Association when the outcome is continuous

    So when I'd used logistic regression for a yes/no outcome, I used the odds ratio. Odds ratio could also be obtained by exponentiating the parameter...

    Started by StatsClue‎, 01-01-2012 09:25 PM
    • Replies: 6
    • Views: 4,414
    01-02-2012, 05:51 PM Go to last post
  20. findout if analysis method has an effect on the measured values

    I have 5 blood samples, and have measured the level of "protein CRP" in each blood sample by two different biochemical methods. all 5 blood samples...

    Started by florita‎, 01-02-2012 09:08 AM
    • Replies: 0
    • Views: 1,324
    01-02-2012, 09:08 AM Go to last post
  21. Basic stats question for scientific paper

    Hello, I am writing a scientific paper and have only a basic knowledge of statistics. I was wondering if anyone could help me out to make sure...

    Started by premed‎, 12-27-2011 06:42 PM
    • Replies: 7
    • Views: 4,037
    12-29-2011, 09:26 PM Go to last post
  22. Interaction terms

    I am writing my first clinical research paper and I am teaching myself statistics and SPSS. I have found that there is a correlation between...

    Started by Researcher‎, 12-26-2011 01:43 PM
    • Replies: 2
    • Views: 2,072
    12-28-2011, 11:44 AM Go to last post
  23. Sample size for repeated measures anova

    Hello, I need a formula for a minimum sample size for a repeated measure anova. I couldn't find any online. I am at a preliminary stage in...

    Started by NN_STAT‎, 12-27-2011 08:00 AM
    • Replies: 3
    • Views: 7,768
    12-27-2011, 01:22 PM Go to last post
  24. logistic regression - naive question

    Hello all. I am a doctor, and I am analysing some data regarding survival of some patients. I am still learning the ropes when it comes to...

    Started by tonytheviking‎, 12-23-2011 01:51 AM
    • Replies: 2
    • Views: 2,374
    12-23-2011, 07:22 AM Go to last post
  25. proc glimmix for paired sample

    I'm analyzing a study where we collected baseline and followup data across different sites and across different cities. The questions have binary...

    Started by Qcv2011‎, 12-21-2011 08:12 PM
    • Replies: 0
    • Views: 2,754
    12-21-2011, 08:12 PM Go to last post
  26. Longitudinal vs. Repeated Measures

    Hello, I have a silly question....what is the difference between repeated measures anova and longitudinal analysis ? isn't repeated measures a...

    Started by NN_STAT‎, 12-21-2011 04:51 AM
    • Replies: 4
    • Views: 3,675
    12-21-2011, 06:02 PM Go to last post
  27. Error bars and split-plot design

    I have the following experimental design : Sampling is carried out on three random sites (Factor Site is coded : Site1, Site2, Site3). Within each...

    Started by Johnijohn‎, 12-20-2011 02:18 AM
    error bars, split-plot
    • Replies: 0
    • Views: 1,717
    12-20-2011, 02:18 AM Go to last post
  28. Methods in longitudinal analyses with different follow-up times

    Hi all, I am new to this forum, but registered because I am looking for the right method to use in the analyses of two different projects, both...

    Started by maksler‎, 12-16-2011 03:09 AM
    follow-up, longitudinal design, model selection, repeated measures, unbalanced
    • Replies: 0
    • Views: 1,723
    12-16-2011, 03:09 AM Go to last post
  29. What test to use!?

    I have a data set in which I want to test if there is a difference between the means of a continuous variable for three categories of an ordinal...

    Started by nicklt‎, 12-14-2011 10:18 AM
    • Replies: 0
    • Views: 925
    12-14-2011, 10:18 AM Go to last post
  30. Allowing for time-dependent covariates in power calculations

    Hi all, I'm familiar with how to undertake a power calculation to estimate sample size in an unmatched case-control study. Sample size will be...

    Started by dhj_davis‎, 12-12-2011 01:12 PM
    • Replies: 0
    • Views: 1,739
    12-12-2011, 01:12 PM Go to last post
  31. Questions in ecological data

    Hello everybody, I am trying to compare a variable between two animal subspecies. I've obtained 12 samples from 4 populations of each subspecies (3...

    Started by wingdx‎, 12-09-2011 09:36 PM
    • Replies: 5
    • Views: 2,047
    12-10-2011, 12:12 AM Go to last post
  32. Smile Which method i have to use?

    Dear my friend. I am working on research on supplement. I have 4 group in creatine supplement and placebo ( creatine+ exercise, creatine+ no...

    Started by ali127‎, 12-09-2011 06:47 PM
    • Replies: 4
    • Views: 2,505
    12-09-2011, 11:11 PM Go to last post
  33. Question Newbie searching for providential help

    I have a simple design experiment in which plants were challenged for growth against volatile compounds. Plant growth has been monitored according to...

    Started by killincat‎, 12-07-2011 06:54 AM
    • Replies: 0
    • Views: 1,716
    12-07-2011, 06:54 AM Go to last post
  34. Outlier detection in Affymetrix samples

    Hello everybody, I have a little question concerning the mixing of robust and '"regular" statistics and hopefully you can help me on this topic (I...

    Started by bontus‎, 10-05-2011 05:03 AM
    • Replies: 6
    • Views: 3,959
    12-06-2011, 05:50 AM Go to last post
  35. Method Comparison

    I have four methods of measuring the same thing that I want to compare. If it was just two methods I was comparing I would use a Bland-Altman plot...

    Started by nicklt‎, 12-02-2011 09:23 AM
    • Replies: 0
    • Views: 1,446
    12-02-2011, 09:23 AM Go to last post
  36. Unhappy behaviour comparisons at two sites

    Hello, I have the frequencies of different behaviors of individuals for two sites. I have the individual frequencies for each nest observed i.e....

    Started by Dragonwalker‎, 11-30-2011 04:57 PM
    • Replies: 0
    • Views: 1,065
    11-30-2011, 04:57 PM Go to last post
  37. Sensitivity and Specificity and explained variance.

    Hi. I have one dependent variable (Y) which is binary. I have this data for 100 subjects. I want to generate binary data for 3 independent...

    Started by sammyj‎, 11-29-2011 11:46 AM
    explained variance, generate data, sensitivity, specificity
    • Replies: 0
    • Views: 2,015
    11-29-2011, 11:46 AM Go to last post
  38. Which test use in an genetic association study Help urgent!!!

    Hi!! I'm studing a polymorphic gene. I found 22 different forms of this gene (22 alleles). Now I need to compare 2 parameters between patients and...

    Started by Patigene‎, 11-29-2011 09:38 AM
    association study, gene polymorphism
    • Replies: 0
    • Views: 946
    11-29-2011, 09:38 AM Go to last post
  39. comparing the composition of a transect line

    hi im am looking for guidance on which test to use as i'm not too familiar with biostatistics. as part of my experiment i am testing for...

    Started by kbentley_1‎, 11-28-2011 07:23 PM
    • Replies: 0
    • Views: 1,213
    11-28-2011, 07:23 PM Go to last post
  40. dealing with a don't know response in case control study? Please help

    I want to ask how can we treat the don't know response in case control study. For examples the participants were asked about their frequency of clean...

    Started by medsonia‎, 11-28-2011 06:12 AM
    • Replies: 1
    • Views: 1,880
    11-28-2011, 05:09 PM Go to last post
  41. Temporal replicates

    I have been searching around for an explanation of how to deal with multiple measurements from the same replicate and having no luck... I am...

    Started by amw2320‎, 11-28-2011 10:34 AM
    • Replies: 0
    • Views: 1,596
    11-28-2011, 10:34 AM Go to last post
  42. biostatistic

    . A diabetes clinic in Nottingham decided to invite all of their patients aged between 30 and 65 for a routine health check. Of the 2674 patients who...

    Started by tariq_sohaib‎, 11-27-2011 03:56 AM
    • Replies: 2
    • Views: 2,438
    11-27-2011, 07:29 PM Go to last post
  43. Classification??

    I have been asked to run some stats for someone. In simple description I have a scatterplot where there are three groups of of data (each represents...

    Started by gopher‎, 11-27-2011 01:28 AM
    • Replies: 2
    • Views: 1,356
    11-27-2011, 04:13 PM Go to last post
  44. biostatistic

    Dataset contains the weights in pounds for players in five American football teams obtained by random sampling. Using statistical analysis what can...

    Started by tariq_sohaib‎, 11-27-2011 04:22 AM
    • Replies: 1
    • Views: 2,236
    11-27-2011, 05:25 AM Go to last post
  45. completely lost

    Hi, I was given this question recently and have been scratching my head. This is the question, verbatim: The results of a clinical trial are:...

    Started by jamesmartinn‎, 11-24-2011 01:00 AM
    • Replies: 6
    • Views: 2,741
    11-25-2011, 06:21 PM Go to last post
  46. Comparing demographics characteristic proportions

    Hello, I'm a total beginner looking for some advise about comparing proportions... I have a nationally representative data set from a health...

    Started by lucyg‎, 11-25-2011 01:46 PM
    • Replies: 1
    • Views: 2,770
    11-25-2011, 05:25 PM Go to last post
  47. One way or Two way ANOVA..I am confused.

    Hello I need to evaluate my molecular genetics experiment results. Outline of the experiment is as below. I have four mice groups. Group 1:...

    Started by anchusa‎, 11-25-2011 05:11 AM
    • Replies: 2
    • Views: 2,775
    11-25-2011, 10:33 AM Go to last post
  48. Interpreting main effects in long. mixed model when interactions w/ time are in model

    I am running a mixed effects longitudinal model with linear and quadratic time effects and a continuous outcome. I have a covariate that has a...

    Started by jax‎, 11-25-2011 09:22 AM
    interaction, longitudinal study, means, mixed models, time
    • Replies: 0
    • Views: 2,271
    11-25-2011, 09:22 AM Go to last post
  49. Sample Size

    Hi Guys, I have a complicated question regarding sample size. I have a dataset from a clinical trial, that was collected to check if some...

    Started by NN_STAT‎, 11-23-2011 04:50 AM
    • Replies: 2
    • Views: 2,119
    11-23-2011, 10:02 AM Go to last post
  50. Wink help

    Hello, I am currently working on my phd thesis in neuroscience and need a little bit of help with the statistics.... I have a measure called...

    Started by maya25‎, 11-23-2011 06:55 AM
    • Replies: 0
    • Views: 1,521
    11-23-2011, 06:55 AM Go to last post
  51. Help w/hmwrk

    Mean 3400 and sd is 700g of birthweights...what is the probability of a low birth weight child where low birth weight is defined as < or = to 2500g?...

    Started by penny‎, 11-20-2011 01:20 PM
    • Replies: 0
    • Views: 1,746
    11-20-2011, 01:20 PM Go to last post
  52. Standard Errors of K-M Estimates

    Dear biostatisticians, How do we work out the standard errors of the K-M estimates manually. What is the formula to compute it? I have attached...

    Started by ledzep‎, 11-18-2011 08:17 PM
    • Replies: 1
    • Views: 2,051
    11-20-2011, 12:16 AM Go to last post
  53. Please help!

    What are the values of the deciles of the standard normal distribution that is the 10th-90th% ?

    Started by penny‎, 11-19-2011 11:55 AM
    • Replies: 3
    • Views: 2,220
    11-19-2011, 01:53 PM Go to last post
  54. A tough question: How can I compare 2 sets of coordinates?

    Dear All Please help! I have a set of data for children examined for an eye condition (n=334) All children were examined at 35 weeks of age...

    Started by SiBorg‎, 11-19-2011 05:03 AM
    • Replies: 4
    • Views: 3,703
    11-19-2011, 06:21 AM Go to last post
  55. Multinomial count table - testing for diagonal

    Hi, I have a small amount of knowledge with GLMs. If anything sounds off... Well, it probably is. That said - I have multiple datasets, each with...

    Started by Qroid_mtl‎, 11-18-2011 09:23 AM
    • Replies: 0
    • Views: 1,271
    11-18-2011, 09:23 AM Go to last post
  56. Factor analysis for stroke

    Dear all, can I use factor analysis to analyse which factors are contribute in stroke development (outcome variable)? Which type of variables need...

    Started by cherry25‎, 11-17-2011 09:57 AM
    • Replies: 0
    • Views: 1,630
    11-17-2011, 09:57 AM Go to last post
  57. longitudinal mixed model troubles

    I have growth data for 5 time points. In my unconditional model the quadratic trend best fits the data (likelihood ratio test). However, the random...

    Started by jax‎, 11-16-2011 01:38 PM
    longitudinal study, mixed effects models, random effects
    • Replies: 1
    • Views: 1,598
    11-16-2011, 08:28 PM Go to last post
  58. Analyzing experimental count data with confounding variables

    Hi all, I'm having trouble analyzing my data using the simple statistics that I know, because there are a lot of variables that seem to interact....

    Started by kmgrande‎, 11-16-2011 01:39 PM
    • Replies: 0
    • Views: 2,120
    11-16-2011, 01:39 PM Go to last post
  59. Exclamation something similar to ANOVA for count data?

    Hi. I'm a bit stuck.. Any advice on which tests to use would be very welcome! I am surveying oilseed rape to look at pollinator assemblages & find...

    Started by Sammy‎, 11-16-2011 08:39 AM
    • Replies: 0
    • Views: 1,953
    11-16-2011, 08:39 AM Go to last post
  60. Longitudinal Data Analysis

    Hi! Does anybody have a link or reference to a discussion conerning outcome variables in longitudinal data analysis? Specifically, in some applied...

    Started by jamesmartinn‎, 11-14-2011 07:53 PM
    • Replies: 3
    • Views: 2,758
    11-15-2011, 11:11 PM Go to last post

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