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# Forum: Biostatistics

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

1. ### Predicting outcome with multiple groups

Hi everyone, I'm currently working with 3 different groups (3 disease populations) and I would like to predict which of the three groups they fall...

• Replies: 4
• Views: 112
Yesterday, 03:45 PM
2. ### Finding data given sample mean and variance

Hello, I have a problem, I am given the sample size, mean, variance, and I know it is normally distributed. The question states that 160...

• Replies: 2
• Views: 147
03-27-2017, 09:56 PM

might sound silly but for my research topic I am looking into insulin resistance (IR) and dietary factors. We are measuring IR by the use of...

• Replies: 1
• Views: 111
03-27-2017, 10:23 AM
4. ### Confidence interval question

Fr a sample of 100 hypertensive patients, we find that a 95% confidence interval of systolic BP to be . What statement is FALSE? A- if a drug is...

• Replies: 1
• Views: 110
03-27-2017, 02:20 AM
5. ### reference interval determination

Hi all, I was wondering if I could ask for some help from some more statistically inclined persons than myself. We are trying to determine a...

• Replies: 0
• Views: 89
03-25-2017, 10:23 AM
6. ### Dealing with Log(0)

Dear all, I’ve been stuck for quite some time with a problem that relates to use of log-scale with values that equal zero. My data comes from an...

• Replies: 2
• Views: 210
03-21-2017, 04:22 PM
7. ### Sample size calculation for 1:2 matched case-control study

Hi, I have a matched case-control study with 12 cases and two controls for each case. Evaluating our findings, I want to calculate what our sample...

• Replies: 7
• Views: 536
03-17-2017, 08:59 AM
8. ### stratified log-rank test and proportional hazards

Does stratified log-rank test overcome problem of violation of proportional hazards? I encountered a randomized controlled study of a new drug...

• Replies: 0
• Views: 214
03-16-2017, 04:53 AM
9. ### Regarding Maximum Percent different

Dear all, Could you please explain what maximum percent different for continues vital DiaBP data. How to calculate this? Could you any one...

• Replies: 0
• Views: 135
03-14-2017, 07:08 AM
10. ### vision in eyes at different times

Hi everyone, New to the forum and am seeking a bit of guidance as to how to compare vision (visual acuity) between eyes. So I am trying to...

• Replies: 1
• Views: 210
03-13-2017, 02:42 PM
11. ### Adjustment for correlated data in meta-anlaysis

Hi, I'm completing a systematic review and performing meta-anlaysis forest plots. The research question related to the finding of risk factors for...

• Replies: 2
• Views: 239
03-08-2017, 10:07 AM
12. ### interpretation of a negative risk difference

Hi, I am reviewing a cohort study and trying to make sense of the results. When considering mortality they presented their results as a risk...

• Replies: 1
• Views: 239
03-05-2017, 03:02 PM
13. ### 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: 1
• Views: 278
03-04-2017, 09:36 PM
14. ### Comparative study

Im doing comparative study of Kidney disease and Dermatoglyphics. There is a Continuous variable (ridge count) i am assessing Confounding factors is...

• Replies: 2
• Views: 236
03-03-2017, 08:36 PM
15. ### matched pre-post survey analysis help

I have matched pre-and post test data that evaluated our workshop participants using Likert-type items. Meaning, the same people were given the same...

• Replies: 3
• Views: 285
03-03-2017, 07:52 AM
16. ### 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: 1
• Views: 273
03-02-2017, 12:41 PM
17. ### Cox regression to adjust for site effect in multicenter trial

Hello All, Can stratified Cox regression be used to adjust for site effect in multicenter trials? Thank you in advance to all those who reply.

• Replies: 3
• Views: 413
02-28-2017, 04:34 PM
18. ### 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: 297
02-24-2017, 08:56 PM
19. ### 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: 352
02-23-2017, 05:40 AM
20. ### 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: 611
02-22-2017, 12:56 PM
21. ### 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: 289
02-21-2017, 08:08 PM
22. ### 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: 373
02-15-2017, 04:40 PM
23. ### 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: 313
02-13-2017, 07:24 AM
24. ### 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: 298
02-10-2017, 05:57 AM
25. ### 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: 339
02-06-2017, 03:49 PM
26. ### 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: 416
02-06-2017, 03:45 PM
27. ### 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: 675
02-01-2017, 02:28 PM
28. ### 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: 348
01-31-2017, 02:01 PM
29. ### 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: 640
01-27-2017, 03:43 PM
30. ### 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: 545
01-25-2017, 11:08 PM
31. ### 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: 774
01-25-2017, 01:57 PM
32. ### 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: 334
01-25-2017, 10:40 AM
33. ### 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: 365
01-24-2017, 07:05 AM
34. ### 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: 479
01-22-2017, 06:43 PM
35. ### 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: 740
01-22-2017, 09:40 AM
36. ### 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: 548
01-16-2017, 08:06 AM
37. ### 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: 620
01-16-2017, 01:17 AM
38. ### 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: 488
01-15-2017, 06:05 AM
39. ### 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: 790
01-11-2017, 03:50 PM
40. ### 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: 569
01-10-2017, 01:38 PM
41. ### 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: 800
01-08-2017, 01:38 PM
42. ### 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: 1,249
01-03-2017, 03:40 AM

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: 1,032
12-23-2016, 07:08 AM
44. ### 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: 1,181
12-22-2016, 04:05 AM
45. ### 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: 768
12-19-2016, 10:01 AM
46. ### 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: 879
12-16-2016, 10:37 AM
47. ### 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: 949
12-10-2016, 04:55 AM
48. ### 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: 956
12-09-2016, 02:58 AM
49. ### 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: 656
12-07-2016, 12:27 PM
50. ### 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: 1,110
12-06-2016, 10:07 AM
51. ### 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: 789
12-03-2016, 08:56 AM
52. ### 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: 712
12-02-2016, 02:19 PM

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