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Forum: Biostatistics

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

  1. Smile How to stratify an additive hazards model?

    Hi, I am trying to conduct a stratified additive hazards model (Aalen’s additive model). I am using Stata 12.1. The stata syntax for the...

    Started by martina.andersson‎, Today 10:57 AM
    aalen's additive hazards, additive hazards, cox regression
    • Replies: 0
    • Views: 51
    Today, 10:57 AM Go to last post
  2. AMOS 7.0 Student Version

    Hi everybody, I would like to download Amos 7.0 Student version but I couldn't find it anywhere. Could anyone help me please?

    Started by maver37‎, 06-18-2014 12:54 PM
    • Replies: 1
    • Views: 344
    10-15-2014, 04:11 AM Go to last post
  3. ANOVA - floral longevity, seeking feedback on tests performed

    I have done my statistical analysis and would appreciate any feedback to say if my tests are appropriate. If not, what tests would you recommend? I...

    Started by caryophyllus‎, 10-10-2014 11:00 PM
    • Replies: 2
    • Views: 272
    10-13-2014, 05:51 PM Go to last post
  4. Type I and Type II SS for ANOVA, non-statistician

    Good Afternoon (non-statistician here), I have to automate a GLM within an Excel sheet that will be analyzing some toxicity data, resulted from...

    Started by BrainExploding‎, 10-10-2014 12:52 PM
    anova, glm, type i ss, type ii ss
    • Replies: 3
    • Views: 171
    10-10-2014, 02:29 PM Go to last post
  5. Negative Trend

    I am hypothesizing a decrease in a type of injury over the past decade. I have the number of admissions to my hospitals and the number of patients...

    Started by hlsmith‎, 10-09-2014 08:33 AM
    • Replies: 7
    • Views: 216
    10-09-2014, 01:03 PM Go to last post
  6. Post Selecting most consistent gene expression across multiple replicates

    Hi Members, I have microarray data set of genes with the expression value in 3 experiments. I would like to select the genes whose expression value...

    Started by anikng‎, 10-08-2014 12:22 AM
    • Replies: 0
    • Views: 142
    10-08-2014, 12:22 AM Go to last post
  7. Multifactor MANOVA Help

    Struggling mightily with some analyses for my thesis. I am using SAS for this analysis and trying to do MANOVA. I have some time-activity budget...

    Started by featherchaser‎, 10-07-2014 05:47 PM
    • Replies: 0
    • Views: 122
    10-07-2014, 05:47 PM Go to last post
  8. help with Kaplan-Meier curve

    I was trying to make a simple KM curve. The event is the death of cancer patients. The time is the time between diagnosis to last follow up. The...

    Started by sky_yin‎, 09-10-2014 12:33 PM
    • Replies: 1
    • Views: 200
    10-07-2014, 12:25 AM Go to last post
  9. Study review question for all you fellow biostat nerds. :)

    I'm thinking a welch's t-test is appropriate, but unsure of that? Can anyone lead me in the right direction? A geographer studying “hammock...

    Started by bionerdette‎, 10-04-2014 03:06 AM
    • Replies: 1
    • Views: 203
    10-04-2014, 05:49 AM Go to last post
  10. How to calculate correction factor from two sets of numbers

    Hi, Two sets of samples were centrifuges at two different revolutions/sec. I would like to calculate the correction factor for the values...

    Started by madsmad‎, 10-02-2014 02:05 AM
    • Replies: 0
    • Views: 144
    10-02-2014, 02:05 AM Go to last post
  11. Pathway/gene set enrichment: Testing if my target pathway is enriched

    Dear all, I was wondering whether you could help me with the following biostatistics question. I have consulted several people, who gave very...

    Started by Mattijs‎, 10-01-2014 11:16 AM
    • Replies: 0
    • Views: 155
    10-01-2014, 11:16 AM Go to last post
  12. ANOVA on paired data

    Hello all, I am trying to design an experiment, and in order to dig a sample size I need to know how the data will be analyzed. This is an...

    Started by NN_STAT‎, 09-18-2014 03:22 AM
    • Replies: 1
    • Views: 321
    09-27-2014, 09:44 AM Go to last post
  13. Hypothesis Test method Query

    What would be the appropriate statistical method to investigate whether patients who had a history of having drug “X” on a regular basis had...

    Started by GKK‎, 09-25-2014 11:19 PM
    • Replies: 5
    • Views: 342
    09-26-2014, 01:34 PM Go to last post
  14. [SPSS - BLR] Adding interaction term leads to multicollinearity

    Hello, I’m re-analysing survival data from another author Data: 2 Treatments (no controls); 4 Temperatures; Event = Death on day 12...

    Started by lisaclancy‎, 09-26-2014 03:48 AM
    • Replies: 0
    • Views: 160
    09-26-2014, 03:48 AM Go to last post
  15. Sample Size and Power Calculation- Stepped Wedged Design

    Hello, I am looking for an advice on sample size and power calculation for an intervention study. The study uses a stepped wedged design. The...

    Started by Ken Mutai‎, 09-25-2014 04:25 PM
    • Replies: 0
    • Views: 139
    09-25-2014, 04:25 PM Go to last post
  16. Parametric or Non-Parametric and why?

    I want to examine how three different treatments impact cytokine production in primary human cells (n=3) compared to an untreated control (example...

    Started by A.B‎, 09-22-2014 02:41 AM
    • Replies: 9
    • Views: 398
    09-22-2014, 01:20 PM Go to last post
  17. Longitudinal analysis

    I am reading a book on medical analysis using SAS. These questions relate to longitudinal analysis. During a signficant section of the book they use...

    Started by noetsi‎, 09-19-2014 12:52 PM
    • Replies: 8
    • Views: 315
    09-22-2014, 10:34 AM Go to last post
  18. Hierarchical Spatio-temporal modelling

    Is it possible to create a hierarchical spatio-temporal model in a case whereby the age specific population size is not available at any given time...

    Started by juma‎, 09-22-2014 07:59 AM
    • Replies: 0
    • Views: 114
    09-22-2014, 07:59 AM Go to last post
  19. Measuring variability within a system

    Does anyone know of a way to measure the amount of variability within a system to create a "metric" of variability that can then be used in a...

    Started by Austin‎, 09-21-2014 07:35 PM
    • Replies: 0
    • Views: 137
    09-21-2014, 07:35 PM Go to last post
  20. applaying animal behavior algorithms in social science

    Dear Forum, I was hoping that someone could point me in the right direction; a starting point is all I need: In my dissertation I would like to...

    Started by MPtheR‎, 09-16-2014 11:35 PM
    algorithms, social sciences
    • Replies: 2
    • Views: 302
    09-20-2014, 12:28 AM Go to last post
  21. Biometrics

    Average height of tree is 23,2 m with standard deviation of 4,1 m. Draw and calculate above what height is the 10% of the highest trees? Heights are...

    Started by jerdnalesik‎, 09-18-2014 07:54 PM
    • Replies: 1
    • Views: 191
    09-18-2014, 08:01 PM Go to last post
  22. Tobit regression output

    I ran a Tobit regression model looking at the effect of temperature, phosphorus and nitrogen and location on algae units (upper limit of 85 units)....

    Started by bugman‎, 09-15-2014 11:59 PM
    • Replies: 0
    • Views: 167
    09-15-2014, 11:59 PM Go to last post
  23. Unequal variances in ANOVA

    Non-statistician here, looking for help... My data (data from 8 different populations of plants) when analyzed using one-way ANOVA on SPSS v21...

    Started by huertaaj‎, 09-15-2014 01:24 PM
    one-way anova, unequal variances
    • Replies: 2
    • Views: 204
    09-15-2014, 02:44 PM Go to last post
  24. Relative risk

    The following comes from "Applied Medical Statistics Using SAS" 114-115. In it: p1 occurs when a disease is present when a risk factor is present...

    Started by noetsi‎, 09-11-2014 03:25 PM
    • Replies: 10
    • Views: 325
    09-15-2014, 10:36 AM Go to last post
  25. Does anyone know how to run log-rank test in R adjusting both Rho and gamma

    There used to be a package called surv2sample which is no longer supported by R.

    Started by joyrus‎, 09-13-2014 11:40 PM
    • Replies: 0
    • Views: 169
    09-13-2014, 11:40 PM Go to last post
  26. Unclear output logistic regression

    Dear All, I performed a logistic regression with SPSS to determine which factors were associated with a binomial variable. Briefly, the binomial...

    Started by nicoladiggi‎, 09-08-2014 01:47 PM
    • Replies: 6
    • Views: 266
    09-10-2014, 08:51 AM Go to last post
  27. U shaped curve modelling

    Hello, Someone knows how to modelize and test a U shaped curve and if there is a specific procedure in SAS? Thanks for your help!

    Started by didye‎, 09-08-2014 11:48 AM
    u shape; model;
    • Replies: 2
    • Views: 155
    09-10-2014, 07:57 AM Go to last post
  28. Odds ratios lower than 1 for continous variable

    Lets says you want to check the effect of age on a specific event. In the univariate model : event = age, the odds is significantly lower than 1...

    Started by didye‎, 09-06-2014 05:16 PM
    average, odds ratio
    • Replies: 4
    • Views: 211
    09-07-2014, 12:47 PM Go to last post
  29. Help with power calculation!?

    Hi, I have a dataset on a cohort of patients with fixed number of subjects. I have a primary outcome and a primary exposure. If I want to do a...

    Started by leilafg‎, 09-01-2014 01:48 PM
    • Replies: 4
    • Views: 291
    09-04-2014, 04:48 PM Go to last post
  30. Comparing count data and cultivars in R

    Hi, I'm trying to analyse an experiment with this setup: A plant species with 16 different cultivars of 4-5 plants per cultivar (completely...

    Started by hobglobin‎, 09-03-2014 01:45 PM
    count data, glm, r code
    • Replies: 0
    • Views: 161
    09-03-2014, 01:45 PM Go to last post
  31. Incidence rate and Kaplan Meier

    Hello, I have a question about what we call "incidence rate" at the end of a longitudinal study. If there are a number of censored data, how do...

    Started by didye‎, 09-01-2014 08:24 AM
    incidence rate, kaplan-meier
    • Replies: 0
    • Views: 155
    09-01-2014, 08:24 AM Go to last post
  32. Is this possible?

    Hi, I have come stuck on a really simple question. I have access to excel and SPSS. I have a dataset of response to a treatment. Sample size =...

    Started by k093‎, 08-27-2014 10:49 PM
    • Replies: 7
    • Views: 370
    08-28-2014, 04:38 PM Go to last post
  33. sample size recalculation mid-trial based on unplanned look at data

    what is the current thinking on sample size recalculation mid-trial based on unplanned look at the data. suspect futility and want to either stop...

    Started by msecic‎, 08-28-2014 12:52 PM
    • Replies: 0
    • Views: 184
    08-28-2014, 12:52 PM Go to last post
  34. When to use validation and derivation cohort?

    Hi everyone, I was wondering if there is any generic rules on when it's good to use a derivation and validation cohort on a dataset? So far I have...

    Started by dubaifrom‎, 08-28-2014 03:56 AM
    biostatistics, model checking, model validation, modeling techniques
    • Replies: 1
    • Views: 128
    08-28-2014, 08:00 AM Go to last post
  35. Unhappy Who to analyse these data please

    A very short question: I have a group of patients, followed after an operation, and I have collected a number of variables on these patients before...

    Started by Bio_Stat‎, 08-27-2014 10:51 AM
    • Replies: 2
    • Views: 210
    08-27-2014, 02:17 PM Go to last post
  36. comparing means when the control group has 2 subsets of data

    Hi there I have prospective study looking at functionality after an injury; let's say a big toe injury. I have the injured group (N=44) that has...

    Started by keamano‎, 08-25-2014 07:19 PM
    comparing means, multiple comparisons, propective clinical study
    • Replies: 2
    • Views: 210
    08-27-2014, 09:16 AM Go to last post
  37. calculation of sample size for different groups using proportions

    Dear all, kindly help me to arrive a sample population from each village in the study. i would like to do study survey in few villages and how...

    Started by karun sandeep‎, 08-25-2014 04:51 AM
    • Replies: 0
    • Views: 150
    08-25-2014, 04:51 AM Go to last post
  38. Kaplan Meier Curves + Cox PH

    Hi all: I'm doing a survival analysis on a dataset of about 650 cancer patients. The outcome is time to death. Patients are censored when they are...

    Started by jamesmartinn‎, 08-21-2014 07:42 AM
    • Replies: 3
    • Views: 245
    08-22-2014, 01:36 PM Go to last post
  39. not random but justified statistical methods for validating a diet quality index

    Has anyone good advice for validating a diet quality index? I have gone through validation studies and the methods used vary a lot. Some of them do...

    Started by Nutritionist‎, 08-20-2014 03:09 AM
    • Replies: 1
    • Views: 221
    08-20-2014, 09:13 AM Go to last post
  40. multi level categorical variable in a cox model

    Hello everyone, I would like to know which kind of test of significance do you use for categorical variables with more than two levels in a COX...

    Started by didye‎, 08-19-2014 06:39 AM
    categorical variable, cox model
    • Replies: 1
    • Views: 140
    08-19-2014, 07:58 AM Go to last post
  41. plots for hazard ratios / continuous variables

    Hello everyone, Somebody knows which kind of plots could I create to display a set of hazard ratios for continuous variables. I used to use...

    Started by didye‎, 08-18-2014 05:18 AM
    continuous variable, forest plot, hazard ratio
    • Replies: 1
    • Views: 147
    08-19-2014, 07:13 AM Go to last post
  42. Matching 3 groups

    Hello everybody! I have 3 treatment groups and I need to match them on several criteria. However, I don't know the steps to do that, should I...

    Started by abelstat‎, 08-19-2014 04:44 AM
    • Replies: 0
    • Views: 108
    08-19-2014, 04:44 AM Go to last post
  43. Any statisticians out here please? £50 voucher offer

    I am doing a survey as part of my MSc project and need someone to review the protocol from a stats point of view, including helping to determine the...

    Started by brownbabygirl‎, 08-11-2014 03:13 PM
    2 Pages
    1 2
    • Replies: 22
    • Views: 1,030
    08-19-2014, 02:51 AM Go to last post
  44. Interpretation of mixed model results

    Hello all, I need some assistance with interpreting the results of a mixed model and putting up textual conclusions. I ran a mixed model with a...

    Started by NN_STAT‎, 08-18-2014 08:05 AM
    • Replies: 0
    • Views: 135
    08-18-2014, 08:05 AM Go to last post
  45. Ordinal regression vs Chi-Square

    Hey guys, I've finished analyzing my data for an article regarding decompresion in divers. My dependent variable is ordinal - 1-no recovery...

    Started by XPeriment‎, 08-16-2014 04:50 AM
    • Replies: 9
    • Views: 289
    08-17-2014, 01:08 PM Go to last post
  46. Test for linear trend in odds ratio in linear regression

    I often see epidemiological studies where a continuous variable has been divided into quantiles and the odds ratios for each quantile compared with a...

    Started by Disvengeance‎, 07-13-2014 09:50 AM
    • Replies: 9
    • Views: 461
    08-17-2014, 10:14 AM Go to last post
  47. Evaluating data via a three-way (2 x 3 x 4) ANCOVA

    Biomedical researcher here, trying to figure out how to analyze the results of a study on cell culture conditions. Three IVs were chosen: compound A...

    Started by lnhstats‎, 08-15-2014 09:47 AM
    ancova, control, interaction, prettest, timecourse
    • Replies: 6
    • Views: 388
    08-16-2014, 05:56 PM Go to last post
  48. Longitudinal analysis of drug use data

    Hi all, I'm looking to conduct a longitudinal analysis using data from 5 waves of an observational research study. What I'm really interested in...

    Started by omnibus‎, 08-14-2014 12:18 PM
    longitudinal data, modeling techniques, observational study
    • Replies: 4
    • Views: 198
    08-15-2014, 11:09 AM Go to last post
  49. non-comparative retrospective study: sample size calculation required?

    Hallo I am planning a very simple retrospective non-comparative study. The plan is to review patient charts of patients with cancer to determine...

    Started by noob‎, 08-13-2014 10:50 AM
    • Replies: 2
    • Views: 192
    08-15-2014, 05:49 AM Go to last post
  50. intertidal ecology - change in human use over two sampling periods

    Thank you in advance for any advice on this ecological study of human use of rocky intertidal habitats! I am examining the change in the number of...

    Started by intertidalecologist‎, 08-14-2014 04:48 PM
    • Replies: 0
    • Views: 176
    08-14-2014, 04:48 PM Go to last post
  51. DNA comparison: Repeated-measures ANOVA.. but too many parameters to consider?

    Dilemma about which test to correctly use... It's a tricky, confusing, one! I'm looking at DNA extraction methods, here's how I've got the data set...

    Started by Becky‎, 08-11-2014 06:22 AM
    anova, biology, multi, spss
    • Replies: 1
    • Views: 219
    08-14-2014, 10:14 AM Go to last post
  52. Longitudinal Adhesion Test for Patches

    Hello dear colleagues. I have to compare the adhesion of two drugs in the form of transdermal patches. According to EMA's (European Medicines...

    Started by lucasteixeira‎, 08-12-2014 09:35 AM
    longitudinal study, ordinal variable, statistical help
    • Replies: 0
    • Views: 149
    08-12-2014, 09:35 AM Go to last post
  53. Single cohort but comparing two groups WITHIN this cohort

    Hello, I have a single retrospective cohort that was selected over multiple years, without a control cohort (it is not possible to find a control...

    Started by theUmbra‎, 08-10-2014 01:33 PM
    • Replies: 0
    • Views: 128
    08-10-2014, 01:33 PM Go to last post
  54. Hopefully Simple Question: Two Way ANOVA or One-Way Repeated Measures?

    Hi all, I'm new here but have been wrestling with a statistical question for a while now, getting different answers depending who I ask. I'm really...

    Started by molbioadam‎, 08-05-2014 10:00 AM
    • Replies: 3
    • Views: 249
    08-09-2014, 08:31 AM Go to last post
  55. Multilevel Structure & Random Effects

    Hi! We have the following data structure and I'm wanting to get some feedback on how to correctly specify a multilevel model for research. ...

    Started by jamesmartinn‎, 08-05-2014 05:51 PM
    • Replies: 8
    • Views: 493
    08-08-2014, 11:14 AM Go to last post
  56. Classification model according to multivariate presence/absence dataset

    Hi there! I am currently working on the analysis of a two part experiment looking at bacterial communities in diatoms, under different...

    Started by stephiexoxo‎, 07-31-2014 03:06 AM
    classification, ecology, null distribution, presence/absence
    • Replies: 1
    • Views: 220
    07-31-2014, 05:52 PM Go to last post
  57. Response Rates

    Hello! I have a simple question. If I determined that I needed 100 participants to fill our my survey. We had a simple random sampling technique....

    Started by PsychStats_Leb‎, 07-31-2014 01:31 PM
    • Replies: 1
    • Views: 187
    07-31-2014, 03:06 PM Go to last post
  58. COX models and continuous variables

    Hello everyone. I have a simple and basic question about cox model. When I introduce a continuous variable in the model, the hazard ratio assessed...

    Started by didye‎, 07-30-2014 09:16 AM
    continuous variable, cox proportional hazard, survival analysis
    • Replies: 3
    • Views: 243
    07-30-2014, 10:44 AM Go to last post
  59. Required testing for complementary log-log-models

    Hello everybody, I am applying a complementary log-log-model (including time-invariant aswell as time-variant variables). So far I am not really...

    Started by geomo‎, 07-06-2014 07:24 AM
    • Replies: 1
    • Views: 241
    07-30-2014, 07:54 AM Go to last post
  60. non-parametric data for reference ranges

    Hello, I am very new to statistical analysis, but am very excited to to be learning it. I am working on finding reference ranges for some...

    Started by schmidlk‎, 07-28-2014 08:36 PM
    blood tests, medical statistics, new in the field, non-parametric, reference range
    • Replies: 0
    • Views: 195
    07-28-2014, 08:36 PM Go to last post

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