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Forum: Biostatistics

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

  1. repeated measurements - ANOVA, friedmann's test or kruskal wallis?

    Dear all, I am a junior doctor getting involved in medical statistics, of which my knowledge is very preliminary. The problem I face is the...

    Started by vzavvos‎, 10-29-2014 04:25 PM
    friedman, repeated measurements
    • Replies: 0
    • Views: 112
    10-29-2014, 04:25 PM Go to last post
  2. Noob question

    why when modeling do some variables have significant p values yet they are not included in the model ? I was doing a cox regression model and...

    Started by Logician‎, 10-28-2014 06:58 PM
    variables in models
    • Replies: 7
    • Views: 177
    10-29-2014, 03:05 PM Go to last post
  3. Post Fisher test or interaction terms to determine if 2 groups are different

    Hi, I split my sample in 2 groups, participants with condition +M and participants without the condition -M. I calculated correlations and beta...

    Started by DataPilgrim‎, 10-23-2014 02:14 PM
    fisher test, groups, interaction terms
    • Replies: 3
    • Views: 157
    10-29-2014, 01:31 PM Go to last post
  4. Identical continouous dependant variables vs. unique independent variables?

    Hi guys, I'm having an issue re: the statistical test I should be using in research I am undertaking. Let's say I have a study population of...

    Started by Xami‎, 10-28-2014 11:49 PM
    exposure, land use regression
    • Replies: 2
    • Views: 110
    10-29-2014, 08:39 AM Go to last post
  5. T test comparison of 3 treatments

    Good evening, i´ve developed 3 models wich predict the extent of area covered by the studied group. what statistical test could be useful for...

    Started by jos19‎, 10-27-2014 10:16 PM
    no replicas
    • Replies: 1
    • Views: 146
    10-28-2014, 01:52 AM Go to last post
  6. ?Pearson ?point-biserial correlatiom coefficient for relationship between variables

    Hi, I'm new on this forum, thanks for reading my post! I'm trying to figure out if I've used the best method for determining a relationship between...

    Started by waynes‎, 10-27-2014 06:08 PM
    biostatistics, pearson correlation, point-biserial, valid
    • Replies: 0
    • Views: 89
    10-27-2014, 06:08 PM Go to last post
  7. Question 4 proportions to compare, each with separate N and 95% CI. use ANOVA or what?

    With the above info, what's the correct way to determine whether the proportions differ significantly? I thought I had a lovely formula that used...

    Started by StatsIsPain‎, 10-23-2014 07:52 PM
    • Replies: 1
    • Views: 134
    10-23-2014, 09:42 PM Go to last post
  8. 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, 10-20-2014 10:57 AM
    aalen's additive hazards, additive hazards, cox regression
    • Replies: 0
    • Views: 143
    10-20-2014, 10:57 AM Go to last post
  9. 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: 407
    10-15-2014, 04:11 AM Go to last post
  10. 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: 311
    10-13-2014, 05:51 PM Go to last post
  11. 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: 213
    10-10-2014, 02:29 PM Go to last post
  12. 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: 246
    10-09-2014, 01:03 PM Go to last post
  13. 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: 166
    10-08-2014, 12:22 AM Go to last post
  14. 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: 147
    10-07-2014, 05:47 PM Go to last post
  15. 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: 224
    10-07-2014, 12:25 AM Go to last post
  16. 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
    welch's t-test
    • Replies: 1
    • Views: 223
    10-04-2014, 05:49 AM Go to last post
  17. 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: 160
    10-02-2014, 02:05 AM Go to last post
  18. 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: 187
    10-01-2014, 11:16 AM Go to last post
  19. 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: 353
    09-27-2014, 09:44 AM Go to last post
  20. 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: 375
    09-26-2014, 01:34 PM Go to last post
  21. [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: 191
    09-26-2014, 03:48 AM Go to last post
  22. 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: 156
    09-25-2014, 04:25 PM Go to last post
  23. 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: 428
    09-22-2014, 01:20 PM Go to last post
  24. 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: 344
    09-22-2014, 10:34 AM Go to last post
  25. 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: 131
    09-22-2014, 07:59 AM Go to last post
  26. 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: 147
    09-21-2014, 07:35 PM Go to last post
  27. 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: 321
    09-20-2014, 12:28 AM Go to last post
  28. 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: 206
    09-18-2014, 08:01 PM Go to last post
  29. 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: 181
    09-15-2014, 11:59 PM Go to last post
  30. 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: 229
    09-15-2014, 02:44 PM Go to last post
  31. 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: 343
    09-15-2014, 10:36 AM Go to last post
  32. 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: 179
    09-13-2014, 11:40 PM Go to last post
  33. 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: 282
    09-10-2014, 08:51 AM Go to last post
  34. 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: 173
    09-10-2014, 07:57 AM Go to last post
  35. 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: 230
    09-07-2014, 12:47 PM Go to last post
  36. 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: 303
    09-04-2014, 04:48 PM Go to last post
  37. 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: 178
    09-03-2014, 01:45 PM Go to last post
  38. 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: 169
    09-01-2014, 08:24 AM Go to last post
  39. 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: 398
    08-28-2014, 04:38 PM Go to last post
  40. 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: 197
    08-28-2014, 12:52 PM Go to last post
  41. 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: 154
    08-28-2014, 08:00 AM Go to last post
  42. 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: 233
    08-27-2014, 02:17 PM Go to last post
  43. 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: 225
    08-27-2014, 09:16 AM Go to last post
  44. 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: 160
    08-25-2014, 04:51 AM Go to last post
  45. 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: 261
    08-22-2014, 01:36 PM Go to last post
  46. 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: 238
    08-20-2014, 09:13 AM Go to last post
  47. 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: 156
    08-19-2014, 07:58 AM Go to last post
  48. 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: 163
    08-19-2014, 07:13 AM Go to last post
  49. 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: 127
    08-19-2014, 04:44 AM Go to last post
  50. 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: 1,089
    08-19-2014, 02:51 AM Go to last post
  51. 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: 148
    08-18-2014, 08:05 AM Go to last post
  52. 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: 304
    08-17-2014, 01:08 PM Go to last post
  53. 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: 502
    08-17-2014, 10:14 AM Go to last post
  54. 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: 420
    08-16-2014, 05:56 PM Go to last post
  55. 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: 214
    08-15-2014, 11:09 AM Go to last post
  56. 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: 207
    08-15-2014, 05:49 AM Go to last post
  57. 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: 190
    08-14-2014, 04:48 PM Go to last post
  58. 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: 232
    08-14-2014, 10:14 AM Go to last post
  59. 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: 162
    08-12-2014, 09:35 AM Go to last post
  60. 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: 144
    08-10-2014, 01:33 PM Go to last post

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