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Forum: Biostatistics

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

  1. How do I apply the hazard ratios from an existing Cox model to a new dataset?

    Hello all, I have the hazard ratios (about 50) from an existing Cox model of survival based on national data, which calculates expected survival...

    Started by mkbehnke‎, 06-06-2011 09:22 AM
    • Replies: 1
    • Views: 2,599
    06-17-2011, 01:59 PM Go to last post
  2. Pointers for a 2x2 Discriminant Analysis? Can you do multiple DAs on the same MANOVA?

    Hi, I was wondering whether anyone could point me in the direction for help on performing a DA on a two-factor (2 IVs each with 2 groups) design....

    Started by J S‎, 06-08-2011 09:50 AM
    discriminant analysis, interaction term, manova, two-factor
    • Replies: 0
    • Views: 1,888
    06-08-2011, 09:50 AM Go to last post
  3. comparing multiple sequences of data over time

    Hi, would really appreciate help on how to test my data! I've three groups (with 5-8 individuals in each group; actually 5 in one and 8 in each of...

    Started by radia‎, 06-01-2011 02:45 PM
    • Replies: 4
    • Views: 19,646
    06-07-2011, 11:47 AM Go to last post
  4. crossover trial analysis

    I'm trying to analyze a crossover clinical trial with 2 treatment periods: study drug and placebo. I use SAS. I wasn't sure if I should use proc...

    Started by lovesas‎, 10-12-2010 07:34 AM
    • Replies: 2
    • Views: 5,854
    06-03-2011, 10:21 PM Go to last post
  5. effect vs. parameter significance

    In a logistic regression, I have a categorical variable (3 levels) which the type III analysis of effects shows as non-significant (p >.05). Yet in...

    Started by mostater‎, 06-03-2011 02:41 PM
    • Replies: 0
    • Views: 2,501
    06-03-2011, 02:41 PM Go to last post
  6. sample representativeness

    Is there a statistical test to show that a sample is representative of a population? or is just fufilling some criteria, ie sample source, data...

    Started by alr621‎, 06-02-2011 10:11 AM
    clinical study, representative, sampling
    • Replies: 1
    • Views: 3,357
    06-02-2011, 10:55 AM Go to last post
  7. Chi sq? Or what else?

    I need to compare two recombination frequencies, and have previously used heterogeneity Chi Sq tests, but have recently been told that I cannot do...

    Started by janekerye‎, 05-25-2011 09:04 PM
    • Replies: 1
    • Views: 2,170
    06-02-2011, 08:06 AM Go to last post
  8. Exclamation Help with Factor analysis

    Hi, I am new with Factor Analysis, and need help to determint the cut off. For instance; I will measure the knowledge with 10 variable. How would I...

    Started by dinsya‎, 05-11-2011 02:29 AM
    • Replies: 4
    • Views: 3,029
    05-31-2011, 03:53 PM Go to last post
  9. How to do a one-way ANOVA on summary data

    I would like to compare eleven different means std. error using a one-way ANOVA with Tukey's multiple comparisons. This seems like a...

    Started by l3a9k‎, 05-25-2011 12:42 PM
    • Replies: 1
    • Views: 3,806
    05-25-2011, 01:17 PM Go to last post
  10. number of cycles and length of each cycle

    How is it possible to determine the number of estrous cycles in dogs when the occurrence of the cycle is given. For instance, when the...

    Started by saslover‎, 05-23-2011 05:50 PM
    • Replies: 2
    • Views: 3,524
    05-24-2011, 04:32 AM Go to last post
  11. Prevalence Ratio

    I recent stumbled upon a formula for Prevalence ratio which is (observed prevalence)/(Expected prevalence) with Observed prevalence is (Total...

    Started by Sandhya‎, 05-23-2011 11:14 AM
    • Replies: 0
    • Views: 4,785
    05-23-2011, 11:14 AM Go to last post
  12. Which test

    We have 4 groups of subjects. Each group is given a different drug. We measure expression of a protein at time zero and at 3 time-points. We want...

    Started by bears‎, 05-19-2011 05:49 PM
    • Replies: 3
    • Views: 2,335
    05-20-2011, 05:14 PM Go to last post
  13. GzLM for counts or ?

    Hi everyone, I'm trying to figure out how to run an appropriate comparison for clutch sizes of birds. Ultimately, I want to compare clutch size of...

    Started by mogetons‎, 05-14-2011 07:36 PM
    binomial, count data, glm, gzlm
    • Replies: 1
    • Views: 2,316
    05-20-2011, 04:08 PM Go to last post
  14. Odds Ratio and Hazard Ratio - HELP!

    I am trying to figure out how to calculate an estimated hazard ratio associated with a specific variable. I have the estimate and standard errors...

    Started by lca223‎, 05-19-2011 03:10 PM
    hazard ratios, help!, odds ratio
    • Replies: 4
    • Views: 9,149
    05-19-2011, 05:48 PM Go to last post
  15. MAPE has high values

    Have two data sets. One a set of calibrated estimations, another actual values. I am trying to calculate mean absolute percent error for the sets. ...

    Started by whewa‎, 05-19-2011 04:14 PM
    • Replies: 0
    • Views: 4,326
    05-19-2011, 04:14 PM Go to last post
  16. Confusion on what level should data follow normality

    Hi everyone. I'm experiencing some confusion as to what level the data should be normal. For instance, in an unpaired data set, where some...

    Started by joseph.skaf‎, 05-18-2011 10:06 AM
    normality, parametric, transformation
    • Replies: 2
    • Views: 2,541
    05-19-2011, 03:45 PM Go to last post
  17. Comparing means without knowing the raw data of one of the population. Possible?

    Hi I would like to compare some epidemiological findings in my study with similar findings in other studies. The problem is: 1. I don't know...

    Started by victorxstc‎, 05-17-2011 12:37 AM
    • Replies: 4
    • Views: 8,467
    05-17-2011, 11:36 AM Go to last post
  18. Randomized Study

    Suppose a pharmaceutical company wants to conduct a post-marketing clinical trial. It needs to recruit patients through retail pharmacies. Suppose...

    Started by aha123‎, 05-15-2011 03:45 AM
    • Replies: 2
    • Views: 2,143
    05-17-2011, 10:07 AM Go to last post
  19. Simplification of formula in logistic regression

    I have performed a logistic regression analysis including five variables and one outcome. However, I would like to simplify the formula significantly...

    Started by mikkelbrabrand‎, 05-15-2011 09:02 AM
    • Replies: 3
    • Views: 5,032
    05-17-2011, 10:05 AM Go to last post
  20. Is my study case-control or retrospective cohort?

    Hi AFAIK if we split the sample by the exposure, it is retrospective cohort; and if we split it by the disease, it is case control. I am...

    Started by victorxstc‎, 05-09-2011 11:20 AM
    case control, cohort, exposure, study design
    • Replies: 8
    • Views: 12,298
    05-13-2011, 11:18 AM Go to last post
  21. which multivariate proc to use- grouping populatons?

    Hi there, This is my first post to forum. Have big problem. I have data about concentration of three chemicals (three traits) in plants from 30...

    Started by stevanavramov‎, 05-11-2011 05:41 AM
    • Replies: 2
    • Views: 1,966
    05-13-2011, 04:44 AM Go to last post
  22. Smile How can data bellow the lower limit of detection be included in statistical analysis?

    My assay has a lower limit of detection of 10. How do I include data below this point in my analysis? Should I enter them as 10 or 0 or is it not...

    Started by onlineuser‎, 05-12-2011 12:14 AM
    biostatistics, lod, lower limit of detection, simple, statistics help
    • Replies: 1
    • Views: 2,947
    05-12-2011, 09:23 AM Go to last post
  23. Some help with repeated measusre + nested design ANOVA (maybe, I am not sure)

    Hi, there, This is my first post here, and I hope that I can get some help here. It is bit long, so please bear with me. I am currently doing...

    Started by northville‎, 05-11-2011 04:58 AM
    • Replies: 0
    • Views: 1,702
    05-11-2011, 04:58 AM Go to last post
  24. Lightbulb Proc surveylogistic

    Hi, 2 days ago I ask about logistics regression, and LINK gave me a good solution for it. It worked. But then after I compare the result between...

    Started by dinsya‎, 03-11-2011 07:09 AM
    • Replies: 6
    • Views: 5,969
    05-06-2011, 02:06 AM Go to last post
  25. Question TOTALLY Confused

    This paper suggests a measure of association (or correlation) between nominal data. It relies on the use of determinants. The general idea is that...

    Started by SandraM‎, 05-05-2011 09:17 AM
    • Replies: 0
    • Views: 1,856
    05-05-2011, 09:17 AM Go to last post
  26. Repeated measures or not?

    Hi All, I sampled crickets weekly over 5 weeks from the same population, and measured their body size. Half of the crickets were taken from...

    Started by Curseit‎, 05-04-2011 03:39 PM
    ecology, repeated measures
    • Replies: 0
    • Views: 1,635
    05-04-2011, 03:39 PM Go to last post
  27. Goodness of fit

    I have developed a risk scoring system that I'm trying to validate. It was originally developed in one cohort, and I am now validating it in a new,...

    Started by mikkelbrabrand‎, 05-03-2011 07:05 AM
    • Replies: 2
    • Views: 2,729
    05-04-2011, 06:18 AM Go to last post
  28. Poll Poll: Survival Analysis: Cox Proportional Hazards with 4000 indicator variables

    THE SITUATION: I am preparing a 420,008 observation Cox Proportional Hazards Regression model with 4001 indicator variables. The 4001st indicator...

    Started by kmatthews‎, 05-01-2011 09:03 AM
    cox, indicator, survival, valid?
    • Replies: 2
    • Views: 2,356
    05-02-2011, 12:36 AM Go to last post
  29. Calculating AUC using survival data

    Hi, first post. I am interested in calculating the areas under two survival curves (treatment group and control group) in an RCT; actually I am...

    Started by Iphix‎, 05-01-2011 09:16 AM
    • Replies: 0
    • Views: 2,189
    05-01-2011, 09:16 AM Go to last post
  30. Need help: Sample size using hypothesis

    Hello guys! I want to calculate the prevalence of transfusion transmitted viral infection (Here HIV, Hepatitis B and Hepatitis C will be tested) in...

    Started by ozzie77‎, 05-01-2011 01:57 AM
    • Replies: 0
    • Views: 1,496
    05-01-2011, 01:57 AM Go to last post
  31. Question standard errors of between-/within- subject factors

    Hi everyone :wave: I'm studying GEE at the moment and I don't understanding the passage below. Could if anyone kindly explain to me in...

    Started by kcwong5‎, 04-28-2011 09:50 AM
    • Replies: 0
    • Views: 1,987
    04-28-2011, 09:50 AM Go to last post
  32. Permanova design

    Hay , first Q on this forum.. ok so I need to perform a permanova analysis of some data 21 variables (7 species in triplicate) and 7 observations...

    Started by drimley‎, 04-27-2011 11:48 PM
    • Replies: 1
    • Views: 4,248
    04-28-2011, 12:40 AM Go to last post
  33. One-way ANOVA vs repeated measure ANOVA

    I am going to perform an RCT comparing a treatment to a control. The study has 3 time points, namely, pre-treatment, post-treatment, and 1-month...

    Started by jerryno34‎, 04-27-2011 10:12 PM
    • Replies: 1
    • Views: 5,656
    04-27-2011, 10:16 PM Go to last post
  34. Sample size calculation for clinical trial based on odds ratio

    Can anyone help get my head a bit clearer on this one? I have completed a cross-sectional study looking at the prevalence of adherence to a...

    Started by Hughesmd‎, 04-25-2011 05:24 PM
    • Replies: 0
    • Views: 4,411
    04-25-2011, 05:24 PM Go to last post
  35. Transforming z to t values (GLM, different error distributions)

    Hi, I am comparing behavioural data collected at two populations. Generalised linear models were used with a behavioural trait as a response...

    Started by PloverLover‎, 04-21-2011 09:17 AM
    binomial, glm, z to t values
    • Replies: 0
    • Views: 2,025
    04-21-2011, 09:17 AM Go to last post
  36. Lightbulb I need help with the Stats

    Hi, I have data on Hiv and need help with calculating the CI. The information I have are: 1. Estimated number people are infected t.ex. 320 2....

    Started by dinsya‎, 04-21-2011 04:11 AM
    • Replies: 0
    • Views: 1,402
    04-21-2011, 04:11 AM Go to last post
  37. Help on which tests to apply to landscape ecology data

    I am looking for help on which stats to apply to my landscape ecology data. I am attempting to demonstrate that a connectivity index is able to...

    Started by Bevan‎, 04-20-2011 11:36 AM
    • Replies: 0
    • Views: 1,761
    04-20-2011, 11:36 AM Go to last post
  38. I have data, need help with the Stats!

    Hello, I collected data for an ecology project. There are two variables: body size and latitude. Hypothesis: As lat decreases, body size...

    Started by kaptnclutch‎, 04-16-2011 06:32 PM
    • Replies: 2
    • Views: 2,547
    04-18-2011, 01:34 AM Go to last post
  39. Effect Size Calculation (Cohen's D) on adjusted mean differences Options

    Hi there, I try to quantify the results from a test between a treatment and placebo group using Cohen's d evaluated as below; d=((μt-μp...

    Started by JG28‎, 04-13-2011 10:52 PM
    • Replies: 0
    • Views: 6,665
    04-13-2011, 10:52 PM Go to last post
  40. design of a vaccine study

    I am trying to design a vaccine study. The objective of the study is to determine if vaccine exposure contributes to an increased risk in developing...

    Started by chucsp‎, 04-13-2011 07:39 AM
    • Replies: 0
    • Views: 2,588
    04-13-2011, 07:39 AM Go to last post
  41. analysing summary stats

    I have a bimodal distribution in my data. I know that all parametric and non-parametric tests become unreliable with bimodal datasets, and that it...

    Started by mogetons‎, 04-12-2011 08:23 PM
    • Replies: 0
    • Views: 4,052
    04-12-2011, 08:23 PM Go to last post
  42. testing integer data with unequal variances

    Hi! My thesis dataset includes 2 variables (lay date and incubation period) that are integers, non-normal and have unequal variances. I'd like to...

    Started by mogetons‎, 04-11-2011 04:18 PM
    • Replies: 0
    • Views: 2,808
    04-11-2011, 04:18 PM Go to last post
  43. data analysis for retrospective cohort study

    Hi!! Im embarrassed to be asking v basic questions :o I proposed a study topic for my group assignment, looking at cancer rates between...

    Started by niledee‎, 04-08-2011 07:17 AM
    • Replies: 2
    • Views: 9,967
    04-09-2011, 06:13 AM Go to last post
  44. sample size calculation in cox regression

    Anyone can help me to firgure out the sample size calculation in cox regression? Are there any simple formula or calculators for it? Thanks

    Started by jerryno34‎, 03-24-2011 09:11 PM
    • Replies: 1
    • Views: 5,307
    04-08-2011, 01:05 PM Go to last post
  45. Unhappy Repeated measures for 4x crossover design

    I have a four period crossover study where subjects take one of four treatments A to D in four different periods, during each period there response...

    Started by sally_anderton‎, 03-31-2011 09:48 AM
    • Replies: 1
    • Views: 5,699
    04-08-2011, 01:03 PM Go to last post
  46. Chi Square results

    Hi all, any help here will be greatly appreciated.. I have a 2 x2 matrix i have compose from data collected Epibiont NIS on Basibiont NIS = 1...

    Started by shift_540‎, 04-04-2011 01:21 AM
    • Replies: 1
    • Views: 2,764
    04-08-2011, 12:56 PM Go to last post
  47. using a co-factor when comparing two groups?

    Hi, I would like to compare two groups, one treated, one control. Usually, I would simply use a t-test, assuming normal distribution and equal...

    Started by colombeli‎, 04-03-2011 12:18 PM
    anova, co-factor, t-test
    • Replies: 5
    • Views: 5,656
    04-03-2011, 01:41 PM Go to last post
  48. Chi-square?

    Hi I tested if individuals were positive for 3 different pathogens at 4 different point of times. For the analysis I used chi-square test. The...

    Started by hey‎, 03-24-2011 11:03 AM
    • Replies: 1
    • Views: 3,852
    04-02-2011, 02:12 PM Go to last post
  49. One big or two small samples?

    I am sampling for a microbe using a presence/absence detection method near the Poisson limit. Assuming that my method can detect 1 CFU no matter...

    Started by bmiksch‎, 03-23-2011 06:15 PM
    • Replies: 3
    • Views: 2,752
    04-02-2011, 01:54 PM Go to last post
  50. Non-parametric t-test

    Hi Everyone, I have a dataset made up of incubation periods for first-laid and second-laid eggs (nest is the sampling unit) that I want to compare...

    Started by mogetons‎, 04-01-2011 10:48 AM
    • Replies: 8
    • Views: 6,578
    04-01-2011, 02:58 PM Go to last post
  51. Interpretation of Relative risk and confidence interval?

    There were fewer primary events in patients assigned to warfarin than in those assigned to aspirin (24, 18% per year vs 48, 38% per year, RR 048,...

    Started by nana0709‎, 08-28-2010 06:16 PM
    • Replies: 8
    • Views: 32,943
    04-01-2011, 02:10 AM Go to last post
  52. Question Estimating Missing Data - help required!

    Hi Forum I am having trouble trying to find a way of estimating missing data from a project I have been working on and I hope that someone can...

    Started by Entomologist‎, 03-25-2011 08:25 PM
    missing data imputation
    • Replies: 0
    • Views: 2,643
    03-25-2011, 08:25 PM Go to last post
  53. life tables: terminology...

    Hello! I'm working on relative survival and so, I'm using life tables. My problem concerns the terminology linked to these tables. Could you help...

    Started by lilly74‎, 03-14-2011 11:28 AM
    • Replies: 9
    • Views: 5,635
    03-24-2011, 10:15 AM Go to last post
  54. Clinical trial analysis - have I got it right?

    Hello all, I would like to see what the pain of a patient is before and after an opperation. But my data is not fitting the assumptions of ANOVA....

    Started by MissyPausch‎, 03-23-2011 08:02 AM
    anova, transformation
    • Replies: 1
    • Views: 3,083
    03-24-2011, 06:01 AM Go to last post
  55. Comparison of rehosp. data with retrospective review

    I'm a social psychologist at a nonprofit organization for people with cerebral palsy and other disabilities. We're anticipating a two-year project...

    Started by krobey‎, 03-23-2011 08:07 AM
    • Replies: 2
    • Views: 2,332
    03-23-2011, 08:12 PM Go to last post
  56. Markov Chain Epidemics

    Hello everyone! I want to model a generalized SIR epidemic in a closed population using a discrete time markov chain. The susceptibles become...

    Started by CraigSager‎, 03-22-2011 07:02 AM
    markov epidemics discrete
    • Replies: 0
    • Views: 2,578
    03-22-2011, 07:02 AM Go to last post
  57. inter-rater agreement: uses of kappa, pearson's, and intraclass coefficients

    Hi everyone: I really appreciate all of the great posts on here! I'm trying to wrap my head around a couple of things. First of all, a bit of...

    Started by reevesfs‎, 03-22-2011 03:56 AM
    interrater agreement, intraclass, kappa, pearson's
    • Replies: 0
    • Views: 3,058
    03-22-2011, 03:56 AM Go to last post
  58. Comparing two data sets and showing them to be from the same source

    I have been searching for a while for the correct type of statistical analysis to do on my data, but I'm not even sure what keywords to be searching...

    Started by Kateh‎, 03-21-2011 10:25 AM
    • Replies: 5
    • Views: 7,507
    03-21-2011, 02:48 PM Go to last post
  59. Nested vs. 2-Way ANOVAs

    Hi! I'm conducting analyses on my MSc data set, and am a little confused about how to think about my data in terms of statistical tests. I have...

    Started by mogetons‎, 03-20-2011 01:59 PM
    2-way anova, anova, nested
    • Replies: 0
    • Views: 4,540
    03-20-2011, 01:59 PM Go to last post
  60. Mortality rates

    Hello guys: I have the actual mortality rate and the predicted morality rate for a group of patients. Is there is a statistical method to get...

    Started by scerab‎, 03-19-2011 09:09 AM
    • Replies: 1
    • Views: 3,134
    03-19-2011, 06:03 PM Go to last post

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