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# Forum: Biostatistics

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

1. ### Test negative factors among correlated determinants

Dear all, I am working on the obesity research. I found a molecule A that is negatively control the generation of adipocytes. I have a cohort of...

• Replies: 0
• Views: 104
02-25-2017, 12:05 AM
2. ### Analysis of Repeated Measures Study with Unequal Time Between Measurements

Hello Everyone, I have inherited the analysis of a study from a previous research student. I am having trouble determining what type of analysis...

• Replies: 1
• Views: 163
02-24-2017, 09:56 PM
3. ### Moran's I Spatial Autocorrelation. Interpreting results.

I have carried out a Moran's I test on the residuals of a GLM model in the "ape" package in R which has returned the output below: Observed:...

• Replies: 1
• Views: 129
02-23-2017, 06:40 AM
4. ### Correct application of multiple testing methods in projects with several experiments

Hi! I have a problem with evaluating how I should correct my alpha and conduct statistical texts when I have several different exeriments in the...

• Replies: 0
• Views: 83
02-23-2017, 04:32 AM
5. ### ADjusting for variables in regression model

Dear all, I'm comparing two populations of oncologic patients that were treated with two different regimens in two different hospitals, group A of...

• Replies: 6
• Views: 392
02-22-2017, 01:56 PM
6. ### Can I combine univariate and multivariate HR?

Hi guys. I'm doing a meta-analysis of survival based on a blood marker, and not all the studies have provided a multivariate hazard ratio. Some have...

• Replies: 6
• Views: 168
02-21-2017, 09:08 PM
7. ### Categorical Variable with Repeated Data Points

Hello, I have some data (continuous DV, nominal IV), that I would like to run an ANOVA or regression on. Strictly speaking, I have 3 levels, but...

• Replies: 1
• Views: 214
02-15-2017, 05:40 PM
8. ### Clinical decision interval

Hi all, I have a question regarding clinical decision intervals (grey zone). We have developed a new screening test and we want to provide the...

• Replies: 1
• Views: 200
02-13-2017, 08:24 AM
9. ### Assessing covariates to include in model

Hi all, I have a couple of basic questions which would be great to get some help on I have a continuous outcome (brain volume: total and divided...

• Replies: 2
• Views: 171
02-10-2017, 06:57 AM
10. ### propensity matching and ITT for cohort study

I am reviewing a cohort study that used a retrospective database to determine if treatment with hypothermia post cardiac arrest improves survival to...

• Replies: 0
• Views: 176
02-06-2017, 04:49 PM
11. ### fixed vs mixed random effects model

greetings, I am reviewing some meta-analysis and have a question regarding fixed vs random effects models. 2 reviews have used basically the same...

• Replies: 4
• Views: 254
02-06-2017, 04:45 PM
12. ### Compensate for correlated observations

Dear users I have an issue that I am not to solve alone and I am here to ask for your help. I work in the ophthalmology field and I have a group of...

• Replies: 4
• Views: 424
02-01-2017, 03:28 PM
13. ### Proper analysis method for dataset involving multiple sessions

I have a dataset that was collected over 5 discrete sessions, with each session collected on a different date. During each session, 10 human subjects...

• Replies: 0
• Views: 217
01-31-2017, 03:01 PM
14. ### Ratio between control and treatment siginificantly different than 1

I would like to know what kind of test I can use to verify my findings. In general I have a two group of people. One is a control group the other one...

• Replies: 2
• Views: 340
01-27-2017, 04:43 PM
15. ### Equivalence test or non inferiority test for non parametric data using stata or spss

I am doing a retrospective study about a new medical device, comparing it with an older device. the first group has 18 cases and the other group has...

• Replies: 4
• Views: 305
01-26-2017, 12:08 AM
16. ### McNemar or Chi sqared test for case-control study

Dear all, I'm facing a dilemma which test would be appropriate to compare frequency of a feature in two age, sex and...

• Replies: 5
• Views: 499
01-25-2017, 02:57 PM
17. ### Issues with ANOVA and bounded variables (percentages)

Hey all, I’m new here. I have an issue with a percentages and the use of ANOVA. But let’s start from the beginning. I m a PhD Student and I study...

• Replies: 0
• Views: 175
01-25-2017, 11:40 AM
18. ### How to combine more datasets

Hi everyone, I’m quite sorry for this very “beginner question” , but I’m stuck on it from several days. I got three experimental groups, four...

• Replies: 1
• Views: 199
01-24-2017, 08:05 AM
19. ### Evaluation of correlation trend

I would like to ask you for help and advice regarding one comment I received during the peer-review process for manuscript I submitted. My colleagues...

• Replies: 1
• Views: 280
01-22-2017, 07:43 PM
20. ### Clinical Trial Simulator - Your feedback is welcomed!

Hi all I hope it's alright if I introduce my clinical trial simulator app here. It's free and you can use it online to simulate a trial, check it...

• Replies: 4
• Views: 498
01-22-2017, 10:40 AM
21. ### Shiny App - Forest Plots

Hi I've created a shiny app a while back that will create forest plots based on user supplied data through (a) uploading a data file (b)...

• Replies: 0
• Views: 314
01-16-2017, 09:06 AM
22. ### correlation study - Is my sample size too small?

Hi there! i'm a pediatrician working in the neonatal ward, and i've recently finished aquiring data about a study that i'm doing - i'm trying to...

• Replies: 4
• Views: 353
01-16-2017, 02:17 AM
23. ### Multilinear regression?

Hi, all: I need help for my research. I would like to develop an analytical method to detect the toxin A metabolites in exposed human urine; I...

• Replies: 1
• Views: 289
01-15-2017, 07:05 AM
24. ### Power analysis with one and two variables?

Hi gang, I am severely illiterate in stats and so am struggling with what would seem to be a very straightforward problem. My problem: We...

• Replies: 1
• Views: 521
01-11-2017, 04:50 PM
25. ### Question on Odds ratio

Hi, I have a basic understanding of odds ratio. I can't figure out how to integrate the space S into my odds ratio equation. For the following...

• Replies: 2
• Views: 315
01-10-2017, 02:38 PM
26. ### What statistical test to use for species abundance between wet and dry season?

Sorry if this question is trivial, I have a collection of camera trap data of recorded species during the rainy season and the dry season. I am...

• Replies: 5
• Views: 480
01-08-2017, 02:38 PM
27. ### Temporal Distribution of Death

Dear all, I plan to conduct a study. The preliminary aim is to examine the temporal distribution of death of terminal cancer patients in hospice...

• Replies: 10
• Views: 856
01-03-2017, 04:40 AM
28. ### Add AUCs

I want to add Area Under the Curve (AUC) from multiple meta analyses. AUC for each Meta analysis is given. How can I add them together?

• Replies: 6
• Views: 690
12-23-2016, 08:08 AM
29. ### Patterns in DNA, seperating signal from noise -- outliers?

Hello all, I'm looking at patterns in fragments of RNA. What I need to do is separate the signals from noise in Exons (small regions of DNA/RNA)....

• Replies: 2
• Views: 842
12-22-2016, 05:05 AM
30. ### t-test or z-test for two proportions?

We did an intervention to reduce the frequency of use of a certain type of treatment and now I want to compare the data pre vs post intervention. ...

• Replies: 3
• Views: 462
12-19-2016, 11:01 AM
31. ### Interpreting Odds Ratios... weird question

Hi, I sort of have a weird question. I have a basic understanding of ORs, and can interpret them, but it's never been clear to me why we...

• Replies: 6
• Views: 598
12-16-2016, 11:37 AM
32. ### Area under Kaplan Meier curve

There is one thing bothering me for some time: What does area under Kaplan-Meier survival curve actally represent? Is there a plausible way to...

• Replies: 0
• Views: 637
12-10-2016, 05:55 AM
33. ### Pooling time points to perform a Fisher test?

Hello, I am currently trying to analyse an experiment to assess if rats with cerebral malformations have a sensitivity deficit on one of their...

• Replies: 4
• Views: 604
12-09-2016, 03:58 AM
34. ### What kind of statistical test can be used for my data?

It is my first post on this forum so please be gentle. If it is not a proper section I would appreciate if moderator moves the thread to the correct...

• Replies: 1
• Views: 431
12-07-2016, 01:27 PM
35. ### How to obtain an unbiased post-stratified estimator for survival probabilities?

Suppose I have estimated the survival probabilities $\hat{S(t)}_1, \hat{S(t)}_2, \ldots, \hat{S(t)}_H$ from $H$ strata. Now I want to get an unbiased...

• Replies: 3
• Views: 831
12-06-2016, 11:07 AM
36. ### Why not use Kaplan Meier?

In the method described here http://dmkd.cs.vt.edu/papers/TKDE17.pdf R code implementation is provided ...

• Replies: 5
• Views: 539
12-03-2016, 09:56 AM
37. ### Bird Community Ecology - BACI experiment

Greetings! I'm currently trying to investigate the impact of an event on the bird community of a National Park on my country. For that I have...

• Replies: 2
• Views: 461
12-02-2016, 03:19 PM
38. ### How to use chi-square test correspondence between features and response in R?

There is a set of tumors,each one includes five features, which relate to one gene type result. Tumor Feature 1 ... Feature 5 Gene type 1 ...

• Replies: 0
• Views: 529
11-27-2016, 12:56 PM
39. ### MDS vs ANOVA / GLM methods - how and why?

Hello to all :wave: I am a new member of this forum and the reason why I ended up here is the following: like many others, I am in desperate need of...

• Replies: 0
• Views: 509
11-26-2016, 06:17 AM
40. ### How the estimate a smple size ?

Hi everybody; I am a PhD student, my thesis focuses on the study of reproductive health among teenagers girls . For that, I'am going to work in...

• Replies: 2
• Views: 546
11-25-2016, 12:15 PM
41. ### Help with linear model

Hi guys, I'm really struggling with the relevant coding for this, I'm using Rstudio. I need a Linear model with Gaussian error structure to find...

• Replies: 1
• Views: 579
11-23-2016, 10:51 AM
42. ### Model Selection in Survival Analysis

I'm having trouble with parametric model selection in survival analysis. I founded this sequence of steps in some presentation. This is an...

• Replies: 1
• Views: 505
11-23-2016, 10:44 AM
43. ### estimating start point of a production of y" -ie findx for y=0 given y values for x>0

I hope I can explain the problem clearly and its not an obvious solution. the application area is say an event (in the body) at say day=0 starts the...

• Replies: 3
• Views: 557
11-23-2016, 04:29 AM
44. ### Help with calculating probability?

I have a strange set of data, it was counting the number of animals entering and leaving a shelter as a 'count' of how many were in the shelter. We...

• Replies: 0
• Views: 444
11-22-2016, 07:55 PM
45. ### Experimental design: Gender comparison in a novel memory matrix.

Hello, I am a medical student who knows very little about biostats and would like some one to tell me whether my analysis for my research makes...

• Replies: 4
• Views: 557
11-22-2016, 07:55 AM
46. ### Proportional hazards and Cox Model

I'm trying to fit a Cox model, but there is some problems. I have the following variables in the model. - Group: 1, 2, ..., 9 - Sex: 1 female...

• Replies: 5
• Views: 910
11-10-2016, 12:42 PM
47. ### Cumulative Incidence with Confidence Intervals when using IPTW

Dear Stata users, I'm doing a time to event analysis with inverse probability of treatment weights(IPTW) estimated with propensity scores from a...

• Replies: 2
• Views: 514
11-10-2016, 12:01 PM
48. ### Help with setting my study!

Hi all, I'm a newbie to biostatistics and I'm trying to figure out how to set the statistical part of my final project. I'm a dentistry student and...

• Replies: 1
• Views: 527
11-08-2016, 09:16 AM
49. ### Parallel and subsequential diagnostic tests

Hey guys, i just ran into a problem: I am having two predictive models: Model 1: Sensitivity: 0.8 Specificity: 0.4

• Replies: 12
• Views: 847
11-08-2016, 02:59 AM
50. ### Dataset for statistical analysis

Dear all, I work in Rome for the Italian National Health Service (www.iss.it); I am currently working on a European clinic project called EMTICS...

• Replies: 4
• Views: 783
11-07-2016, 04:55 AM
51. ### Please help me select the correct statistical test

I'm a general surgery resident and am conducting a quality improvement study about waste in the OR. My statistics background is limited to what I was...

• Replies: 5
• Views: 603
11-07-2016, 02:08 AM
52. ### Medical news story - Is this an OK way to report the stats?

I'm a medical writer covering an upcoming research paper. I'm new to the forum, so please LMK if this is not an appropriate place for my question. ...

• Replies: 2
• Views: 614
11-04-2016, 01:40 PM
53. ### Observed difference between two test for same patient is due to chance?

Hi, I have results from two very sensitive but different lab test trying to find pathogen in a patient sample. For some patients results from two...

• Replies: 0
• Views: 493
11-02-2016, 02:02 PM
54. ### Help with correct model formula for a repeated measures design

Hi there, I will really appreciate some help denoting the proper formula to fit a GLM for the following repeated measures data: I investigated...

• Replies: 0
• Views: 498
11-01-2016, 11:45 AM
55. ### Question about sample size penalty for looking at data mid-trial

Hi, we're running a clinical trial for a skin treatment with a medical device that has a strong effect. We are using an inter-patient control (no...

• Replies: 3
• Views: 692
10-29-2016, 02:08 PM
56. ### Help with regards to deciding appropriate statistical test for success criteria

Hello, I have the collective data of 35 eyes that underwent trabeculectomy surgery for glaucoma control. There is no control group, and...

• Replies: 1
• Views: 523
10-27-2016, 06:00 PM

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