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Forum: Biostatistics

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

  1. 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, Today 08:24 AM
    incidence rate, kaplan-meier
    • Replies: 0
    • Views: 46
    Today, 08:24 AM Go to last post
  2. 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: 248
    08-28-2014, 04:38 PM Go to last post
  3. 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: 129
    08-28-2014, 12:52 PM Go to last post
  4. 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: 68
    08-28-2014, 08:00 AM Go to last post
  5. 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: 132
    08-27-2014, 02:17 PM Go to last post
  6. 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: 149
    08-27-2014, 09:16 AM Go to last post
  7. 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: 97
    08-25-2014, 04:51 AM Go to last post
  8. 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: 174
    08-22-2014, 01:36 PM Go to last post
  9. 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: 160
    08-20-2014, 09:13 AM Go to last post
  10. 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: 93
    08-19-2014, 07:58 AM Go to last post
  11. 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: 80
    08-19-2014, 07:13 AM Go to last post
  12. 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: 61
    08-19-2014, 04:44 AM Go to last post
  13. 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: 737
    08-19-2014, 02:51 AM Go to last post
  14. 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: 72
    08-18-2014, 08:05 AM Go to last post
  15. 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: 198
    08-17-2014, 01:08 PM Go to last post
  16. 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: 346
    08-17-2014, 10:14 AM Go to last post
  17. 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: 256
    08-16-2014, 05:56 PM Go to last post
  18. 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: 148
    08-15-2014, 11:09 AM Go to last post
  19. 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: 126
    08-15-2014, 05:49 AM Go to last post
  20. 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: 118
    08-14-2014, 04:48 PM Go to last post
  21. 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: 165
    08-14-2014, 10:14 AM Go to last post
  22. 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: 105
    08-12-2014, 09:35 AM Go to last post
  23. 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: 85
    08-10-2014, 01:33 PM Go to last post
  24. 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: 188
    08-09-2014, 08:31 AM Go to last post
  25. 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: 342
    08-08-2014, 11:14 AM Go to last post
  26. 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: 172
    07-31-2014, 05:52 PM Go to last post
  27. 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: 145
    07-31-2014, 03:06 PM Go to last post
  28. 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: 185
    07-30-2014, 10:44 AM Go to last post
  29. 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: 193
    07-30-2014, 07:54 AM Go to last post
  30. 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: 146
    07-28-2014, 08:36 PM Go to last post
  31. Question How to interpret residual plot of a logistic regression?

    Hi all, I'm working on a default probability model and was modeling the default probability using logistic regression. The pearson residual and...

    Started by sufeipopo‎, 07-28-2014 02:55 PM
    • Replies: 1
    • Views: 194
    07-28-2014, 03:12 PM Go to last post
  32. Arrow Chi square: Goodness of fit and test of independence

    Ok, so Chi square GOF tests a variable for its fit to a theoretical proportion. Yet, a Chi test of independence does this, for two variables, with...

    Started by TheSloth‎, 07-27-2014 05:19 AM
    • Replies: 0
    • Views: 115
    07-27-2014, 05:19 AM Go to last post
  33. Statistical method to rule out cross-contamination?

    Hello, I hope there is someone who can help me find the right method for my needs. I have conducted a study in which I captured bees at several...

    Started by Bcentralis‎, 07-25-2014 03:32 PM
    • Replies: 0
    • Views: 137
    07-25-2014, 03:32 PM Go to last post
  34. 3D printing project + small sample size (5). How to analyze questionnaire data?

    Hi there, I am currently working on a research project investigating the use of 3D printed patient specific anatomy in pre-operative planning. The...

    Started by stanleyliew‎, 07-24-2014 04:54 PM
    • Replies: 0
    • Views: 202
    07-24-2014, 04:54 PM Go to last post
  35. including items in final version of new instrument

    I have 2 questions I would like advice on. They relate to a paper I'm reviewing for a journal. When developing a new instrument, if you do a...

    Started by MarcelProust‎, 07-22-2014 12:10 PM
    • Replies: 0
    • Views: 134
    07-22-2014, 12:10 PM Go to last post
  36. fish and seagrass help

    Hello, I'm doing something very similar with seagrass and bare sand substrates fish data and just wondering if you had any luck figuring out how to...

    Started by helbob‎, 07-18-2014 07:59 AM
    • Replies: 5
    • Views: 240
    07-21-2014, 06:04 AM Go to last post
  37. [SPSS] Comparison of Fish abundances over 3 inter-tidal zones and 4 sites.

    Hi there, I'm relatively new to statistical analysis so bare with me... I have a research project that aims to find whether fish species...

    Started by Shaan‎, 04-24-2014 08:32 AM
    • Replies: 2
    • Views: 338
    07-20-2014, 04:30 AM Go to last post
  38. Combining two ORs with the same control group

    Hi everybody. I am doing a meta-analysis of observational studies. As the disease I am working on has different stages, some of the studies reported...

    Started by amirh899‎, 07-16-2014 09:21 AM
    • Replies: 12
    • Views: 272
    07-17-2014, 01:19 PM Go to last post
  39. Correct Order in Repeated-Measures Design

    A group of 8 volunteers performed a task on two different devices and a particular variable was measured. The question to be answered is if there is...

    Started by DaDeKi‎, 07-13-2014 04:26 PM
    • Replies: 5
    • Views: 221
    07-17-2014, 09:48 AM Go to last post
  40. Randomized controlled trial sample size calculation

    Sorry if this is in the wrong thread. I am trying to determine if a research project is feasible to conduct by calculating the sample size needed. ...

    Started by efficientfuel‎, 07-16-2014 02:24 PM
    • Replies: 2
    • Views: 245
    07-16-2014, 04:29 PM Go to last post
  41. When do sample size calculations need to adjust for clustering?

    I am aware that sample size calculations for cluster RCTs must adjust for clustered data. I would like to understand better if such adjustment might...

    Started by mayiara‎, 07-14-2014 04:53 PM
    clustering, power, sample size calculation
    • Replies: 1
    • Views: 215
    07-15-2014, 01:53 AM Go to last post
  42. Relationship Satisfaction short Study participants wanted -

    You must be in a relationship to participate in these studies. You can be anywhere on the planet. This preliminary study should only take anyone a...

    Started by williamsven‎, 07-14-2014 10:44 AM
    • Replies: 0
    • Views: 158
    07-14-2014, 10:44 AM Go to last post
  43. which statistic test should I use

    Hello, I have a problem in picking the right statistic test in my case. I have analyzed the microbial community in one sample with different methods,...

    Started by rigel‎, 07-13-2014 12:26 AM
    • Replies: 0
    • Views: 208
    07-13-2014, 12:26 AM Go to last post
  44. Repeated measures analysis

    I have a data set of 450 subject with each having 3 repeated measurements using a new device. I want to compare these measurements with the gold...

    Started by Bardiya‎, 07-11-2014 08:33 PM
    • Replies: 0
    • Views: 173
    07-11-2014, 08:33 PM Go to last post
  45. malthusian growth statistics

    I've got populations consisting of a mix of two strains. I have the numbers of each strain at t=0hrs and t=24hrs. I have been trying to calculate...

    Started by pstils‎, 07-11-2014 11:33 AM
    evolution, growth, malthusian, selection
    • Replies: 0
    • Views: 119
    07-11-2014, 11:33 AM Go to last post
  46. Directional Statistics

    Is anyone familiar with directional statistics? Circular or spherical? I have a some data that I've never considered before - the distribution of...

    Started by evoeco‎, 07-10-2014 02:01 PM
    • Replies: 0
    • Views: 215
    07-10-2014, 02:01 PM Go to last post
  47. Experimental design and mixed models

    Hello, I want to test effect of PH on larval development. I would like to know what is the best experimental design and statistical analysis. ...

    Started by statah‎, 07-09-2014 06:07 PM
    • Replies: 0
    • Views: 162
    07-09-2014, 06:07 PM Go to last post
  48. 2-way ANOVA or not 2-way ANOVA?

    Hi, I'm currently doing an experiment assessing the effect that 4 different growth mediums have in 3 different O2 concentrations. There are 6...

    Started by Kudu97‎, 07-08-2014 07:09 AM
    • Replies: 1
    • Views: 198
    07-08-2014, 08:51 AM Go to last post
  49. Linear Mixed Effects and interpreting transformations

    Hi, I'm running a hierarchical linear mixed effects model in R (subject is nested in dyad). My dependent variable is a continuous variable. When I...

    Started by jposluns‎, 07-05-2014 03:03 PM
    box-cox, homogeneity, mixed effects model, transformations
    • Replies: 0
    • Views: 169
    07-05-2014, 03:03 PM Go to last post
  50. Nested design

    I am conducting a study investigating the effects of different media treatments on protein expression in cells. I have four levels of media treatment...

    Started by leonsmyth‎, 07-03-2014 06:29 PM
    design
    • Replies: 1
    • Views: 214
    07-04-2014, 06:25 AM Go to last post
  51. Can I use Cox regression in a nested case-control study to get adjusted risk ratios?

    I have 70 patients who died suddenly and I've drawn 140 controls for these patients (2:1 matching on age, gender, coronary artery disease and...

    Started by tkentta‎, 06-17-2014 09:57 AM
    • Replies: 1
    • Views: 360
    06-29-2014, 10:43 AM Go to last post
  52. 2-way Anova design repeated across an extra factor. Which approach is the best?

    Hello to everybody, I am a student working on a trial experiment to find the best combination of growing media, fertilizer application and...

    Started by Augustas‎, 06-28-2014 10:52 AM
    • Replies: 0
    • Views: 261
    06-28-2014, 10:52 AM Go to last post
  53. Comparing sex ratio's in 3 different areas and comparing to 50/50 sex ratio

    I'm having a little trouble with some the stats for a project i'm doing. I haven't taken it in years. I need to compare the sex ratios in 3 areas...

    Started by Biology‎, 05-22-2014 09:39 PM
    pearson chi square test
    • Replies: 6
    • Views: 450
    06-27-2014, 04:24 PM Go to last post
  54. interpreting multi-level logit model

    Hi, I posted this in the psychologiy statistics forum as well, but haven't gotten a response. I thought maybe it would fit better here. I have...

    Started by winnie1825‎, 06-26-2014 01:46 PM
    logistic multilevel, multi level, multilevel model, stata output
    • Replies: 0
    • Views: 195
    06-26-2014, 01:46 PM Go to last post
  55. Probability distribution of all possible combinations

    Hi to everybody! I would ask an advice on an analysis that I want to do. I have n=69 balls, within 69, 17 are black balls, 29 white balls, 22...

    Started by xgabrix‎, 06-23-2014 11:58 AM
    combinations, probability distribution
    • Replies: 0
    • Views: 222
    06-23-2014, 11:58 AM Go to last post
  56. Using Repeated Measures ANOVA

    We have just finished an experiment, where we had samples distributed into 6 groups and each group receiving a different treatment. Each group had 5...

    Started by theblackalchemist‎, 06-22-2014 11:10 AM
    • Replies: 0
    • Views: 300
    06-22-2014, 11:10 AM Go to last post
  57. Application in Medicine: Name Entity Recognition and Relation Extraction

    I am trying to do Name Entity Recognition and relation extraction on clinical text notes. Since this domain is specific, I have couple of questions:...

    Started by Xin 61‎, 06-21-2014 04:15 PM
    medicine, ner, relation extraction
    • Replies: 0
    • Views: 180
    06-21-2014, 04:15 PM Go to last post
  58. Survival Analysis: Unequal Follow-up Time

    Hi! I wanted to get some feed back for a study idea that's in the works. I haven't done much applied work in survival analysis, so hopefully you...

    Started by jamesmartinn‎, 06-09-2014 01:55 PM
    • Replies: 4
    • Views: 414
    06-18-2014, 07:40 PM Go to last post
  59. Reconciling differences seen in survival (log-rank vs logistic regression)

    Doing survival analysis on an intervention that has been shown to significantly improve overall survival (OS) in previous studies (time and again). ...

    Started by noviceguest‎, 06-10-2014 11:07 AM
    • Replies: 1
    • Views: 246
    06-18-2014, 05:05 PM Go to last post
  60. 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: 0
    • Views: 190
    06-18-2014, 12:54 PM Go to last post

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