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# Forum: Biostatistics

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

1. ### What test to use?

Hey there, My first post here. I'm currently doing a course in uni which just goes through basic statistics and research methods. I am, however,...

• Replies: 2
• Views: 1,545
09-27-2012, 08:17 AM
2. ### need help regarding statistical methods for a project :(

hi all, i have been tasked to do a biostats project and really need some advice from all the great biostatisticians out there! i have two...

• Replies: 6
• Views: 1,338
09-25-2012, 06:12 AM
3. ### comparing change from baseline (two treatment groups, binomial data)

I am comparing the effectiveness of a vaccine in reducing the prevalence of the targeted protein. I have baseline data (before the vaccine was even...

• Replies: 3
• Views: 4,309
09-25-2012, 05:58 AM
4. ### Which test / model to use ?

Hello I need help choosing the most appropriate test to use: I have 3 groups of treatments, one is the new therapy, one is an active control...

• Replies: 10
• Views: 2,575
09-24-2012, 07:37 AM
5. ### Whether to interpret based on descriptive or infferential statistics in present case?

In our study which is already completed, I have three groups: Drug A(n=87), Drug B(=62) and Drug C(n=5). The Shapiro-Wilk test, Histograms and...

• Replies: 2
• Views: 1,850
09-23-2012, 07:13 AM
6. ### regression analysis

hi. i need advise on how to do regression analysis with a discrete dependent variable and a number of dichotomous and continuous independent...

• Replies: 2
• Views: 1,827
09-21-2012, 09:02 AM
7. ### Weighting multiple responses vs single responses

Hi, I am coding and summing the number of same/similar answers to a semi-open-ended question. While most respondents gave a single response, some...

• Replies: 1
• Views: 2,165
09-21-2012, 08:46 AM
8. ### Sample size formulas

Hello, I find it difficult to find online the formulas for calculating sample sizes for: 1. ANOVA (k means) 2. Mann Whitney U test 3. Non...

• Replies: 5
• Views: 2,709
09-20-2012, 02:30 PM
9. ### Confidence Level for device tests in fda

Hello, I want to know what confidence level is required to be considered for proving a medicine or device is good and it will be great if anyone can...

• Replies: 1
• Views: 1,608
09-20-2012, 04:56 AM

Hello everyone, This is my first post and I really hope someone can help me. I have decided to compare three surgical pathways by collecting data...

• Replies: 2
• Views: 2,110
09-19-2012, 07:08 AM
11. ### Interpreting Cox proportional hazards

I ran a simple cox proportional hazards survival analysis in R using the coxph function in the survival package. For 3 of 9 parameters, the p value...

• Replies: 2
• Views: 2,875
09-17-2012, 02:20 PM
12. ### Correction for multiple comparisons applied to Chi2 value rather than p-value

Hi, I am calculating hundreds of Chi2 and I correct for multiple corrections. The script I am using has a threshold at 400 for the Chi2 value beyond...

• Replies: 8
• Views: 3,587
09-17-2012, 01:44 PM
13. ### Sample size calculations for a study

Hello I need some advice regarding sample size calculations. I need to calculate a sample size for a study testing a new drug. In the study...

• Replies: 0
• Views: 1,488
09-15-2012, 10:53 AM
14. ### [Marine Biology] ANOVA (with unequal variances) statistical test?

I have a pretty complicated data set that I don't know where to start. We sampled intertidal snails through an observation method, at two...

• Replies: 8
• Views: 2,449
09-14-2012, 01:04 AM
15. ### Comparing treatments over time - which test?

Hi, I have been trying to find the effect of different treatments on fruit decay. The experiment: Fruit was monitored for degradation over a...

• Replies: 4
• Views: 3,661
09-13-2012, 10:40 AM
16. ### Comparing two methods to measure disease severity

I am testing a new, fast method to score disease severity in an animal model of a human disease. M appears to be less sensitive than the gold...

• Replies: 8
• Views: 4,768
09-12-2012, 07:20 PM
17. ### Pseudo-time lapse experiment: repeated measures ANOVA??

I am measuring disease severity, using 5 different types of measurements, in animals treated with drug X, over multiple timepoints. The measurements...

• Replies: 0
• Views: 2,315
09-11-2012, 01:47 PM
18. ### This is a nightmare data set

I'll make this brief so there is not too much confusion. I am looking for guidance and advice and generally just to bounce ideas of you guys. We...

• Replies: 7
• Views: 3,775
09-09-2012, 10:22 AM
19. ### clinical trials phase I question on probability of a trial stopping (MTD)

I am given that the P(toxicity given dose) is a logistic function. The model to find the MTD is to first try 2 subjects at Dose 1, and if none...

• Replies: 0
• Views: 1,683
09-08-2012, 09:02 PM
20. ### ROC curve analysis

My question is whether i can apply a ROC curve analysis when I have paired samples i.e., the dichotomous variable 1/0 that identifies pathological...

• Replies: 3
• Views: 2,189
09-07-2012, 11:21 AM
21. ### MANOVAs dependent variables

Hi everyone, I was doing a MANOVA and realised that some of my dependent variables are continuous and some are categorical (with values that are...

• Replies: 0
• Views: 2,124
09-07-2012, 04:00 AM
22. ### Subtype of ANOVA to be used

Hi everyone, I'm struggling a bit in trying to figure out what type of anova to use with my dataset. Essentially I have 10 patients implanted...

• Replies: 1
• Views: 992
09-07-2012, 02:58 AM
23. ### Help to determine the correct statistical method (non-parametric MANOVA?)

I can perform very basic statistics, but I have a serious problem with figuring out what to use in this case. I'm using R (within R Studio) since it...

• Replies: 0
• Views: 2,340
09-04-2012, 12:20 PM
24. ### Test selection help for multivariate response and predictors

I need help determining what method would be applicable to the following situation. There are 2 chemicals, A and B. Also, there are two organisms,...

• Replies: 1
• Views: 1,529
08-31-2012, 02:22 PM
25. ### How to use nonparametric test with repeated measurements and many factors?

Hi, I am investigating the effect of treatment A and B in two different groups of mice (Group A and group B). The outcome is continous (ug...

• Replies: 3
• Views: 3,382
08-28-2012, 09:03 AM
26. ### Heterogeneity test in meta-analysis

Hi everyone, I am trying to do a meta-analysis of ecological data. I would like to do a formal test of heterogeneity between subgroups of a...

• Replies: 0
• Views: 2,752
08-27-2012, 08:23 AM
27. ### which testing should i do?

I have counted bees on four different types of field margins, i have three locations where the field margins where grouped together. What i now...

• Replies: 5
• Views: 1,986
08-23-2012, 02:53 AM
28. ### Test selection for a ‘marks out of 10’ quiz: Binomial, Fisher, meta-analysis, or ?

Hello, I have been testing a type of depth of anaesthesia monitor. It involves listening to the EEG (i.e. it’s an electroencephalophone). It’s...

• Replies: 0
• Views: 19,230
08-19-2012, 12:55 PM
29. ### Non-parametric alternative to repeated-measures ANOVA with a between-subjects factor?

Hello, I'm trying to do a repeated-measures ANOVA but my data is likely violating the multivariate normality assumption. My question is: Does...

• Replies: 4
• Views: 58,830
08-17-2012, 07:50 AM
30. ### Fixed effects vs. Random Effects

Hi we had 5 investigators 1)hand out 100 surveys and 2)record a certain feature of each of the 100 subjects. That feature that they recorded is the...

• Replies: 1
• Views: 1,896
08-16-2012, 08:32 PM
31. ### Which test should I use to compare these two groups?

Hi everybody. I have two groups of doctors, group A and group B. I'm trying to see if there is any statistical difference between them in their...

• Replies: 7
• Views: 2,024
08-16-2012, 02:58 PM
32. ### Job: Health Economist/Economitrician/Biostatistician Required

Health Economist Introduction This is an opportunity to work for an international company specialising in Health Economics, Patient-Reported...

• Replies: 0
• Views: 1,469
08-13-2012, 05:37 AM
33. ### Estimates

Compare point estimate to interval estimate

• Replies: 2
• Views: 1,567
08-10-2012, 07:14 PM
34. ### Durbin-Watson Test

Hi, I'm looking to analyse some vigilance data from monkeys. The data at the moment comes from 5minute samples, but these are separated depending...

• Replies: 3
• Views: 2,492
08-09-2012, 11:49 AM
35. ### ANCOVA violating assumptions

Hi, The data I'm looking to analyse is vigilance data from monkeys. I need to investigate which factors affect the different types of vigilance....

• Replies: 0
• Views: 1,680
08-08-2012, 12:02 PM
36. ### Forecasting "half-time", which method?

My problem: My data is a time-series of watersamples taken daily. The water have a concentration of a toxic pollution and I want to forecast the...

• Replies: 0
• Views: 1,108
08-08-2012, 08:11 AM
37. ### Sample size when comparing 3 groups (proportions)

Problem: I use a common clinical specimen divided equally into two sets with each set to test 3 culture media for growth of a certain organism after...

• Replies: 0
• Views: 2,547
08-06-2012, 03:48 AM
38. ### Discrepencies between SPSS and SAS

Does anyone know why there are differences in results when performing Kaplan Meier survival analysis tests in SPSS and SAS. The values do not match...

• Replies: 8
• Views: 2,296
08-02-2012, 03:28 PM
39. ### biostatistics - command to use for association of fiber intake and cancer

hi everyone can you help me which test i should use ? purpose is to determine the association of intake of dietary-fiber (3 different types of...

• Replies: 1
• Views: 1,634
08-02-2012, 07:25 AM
40. ### Cox Proportional Hazards Regression

Hi, I am hoping someone can help me with which model (frailty, strata or cluster) I should use for my data. I have paired data so I need to take...

• Replies: 1
• Views: 2,623
08-02-2012, 07:25 AM
41. ### Summing Confidence Intervals?

Hello, I have calculated mean concentrations of various environmental chemicals in a population. These chemicals fall into different classes...

• Replies: 2
• Views: 7,092
08-01-2012, 07:08 PM
42. ### Univariate or Multivariate?

Hi My data is on two equal groups of patients. The two groups have roughly equal proportions of males/females. A blood sample was obtained form each...

• Replies: 2
• Views: 1,762
08-01-2012, 06:58 PM
43. ### Sample size calculations

Hi all, I know nothing about sample size calculations, and always feel that this is an area I am lacking in. In general I work with data that has...

• Replies: 5
• Views: 2,426
07-31-2012, 08:32 AM
44. ### MANOVAs

Hi, I’ve performed a MANOVA but cannot perform a box test (because I have fewer subjects per factor than dependent variables). I was wondering if...

• Replies: 0
• Views: 1,442
07-31-2012, 06:25 AM
45. ### Nested/Repeated Comparisons-What test should I use?

Hi! I am having trouble to decide what statistical test to use on my data because I have one factor grouped within another. Here is my...

• Replies: 3
• Views: 1,727
07-30-2012, 10:45 AM
46. ### Characterizing a population

Hello, I have data regarding some new blood test. I have a large sample of 450 patients, all healthy, and I would like to characterize the...

• Replies: 6
• Views: 2,819
07-28-2012, 07:56 PM
47. ### Which test to use?

Hi everyone, I'm working on analyzing some data right now but I'm not sure if I'm even approaching this correctly. I have a master set of data that I...

• Replies: 0
• Views: 1,358
07-27-2012, 08:56 AM
48. ### How to compare paired, non-normal and GROUPED data?

Hi, community, I'm trying to solve this issue using free software on Mac OS X and Ubuntu, namely PSPP (SPSS-compatible), Gnumeric, LibreOffice,...

• Replies: 0
• Views: 1,901
07-27-2012, 01:44 AM
49. ### How to compare repeated measurements

Okay, I have one group of patients. This is a hypothetical example: drug A and B are drugs that decrease puls rate. After application of...

• Replies: 6
• Views: 2,937
07-16-2012, 10:15 PM
50. ### Variance used as dependent variable in logistic regression

Hi all, I'm investigating the factors that contribute to high or low variability in the greenness index of a grassland area over the course of 10...

• Replies: 2
• Views: 1,669
07-12-2012, 04:50 PM
51. ### Propensity Score Matching

Hello, I have retrospective non-randomised data and wish to investigate the relationship between blood transfusions (2 treatment groups :...

• Replies: 3
• Views: 2,103
07-09-2012, 09:04 AM
52. ### Understanding how PFS and other "survival" outcomes are actually defined

Hello, I am trying to better understand how are end points in clinical trials defined when Kaplan-Meier method/log rank test is used. I met this...

• Replies: 0
• Views: 1,782
07-05-2012, 03:53 PM
53. ### groups clustering

Hello everybody, I was wondering about a method to lump a dataset of 20 groups of subjects, each group characterized by a specific mean age, stand...

• Replies: 0
• Views: 1,529
07-05-2012, 12:29 PM
54. ### test to evaluate paired data with 2 ind variables?

Hello, I am conducting a basic preference test experiment to determine whether subjects spend a longer time investigating sample A vs. B, and for...

• Replies: 0
• Views: 1,268
07-02-2012, 12:13 AM
55. ### Impact of age and treatment approach on incidence rates of adverse outcome

In a meta-analysis looking at the impact of age on the incidence of an adverse outcome following treatment for "X", which effect sizes and...

• Replies: 0
• Views: 1,015
07-01-2012, 01:21 AM
56. ### Testing a drug's effect on survival across multiple distinct studies

I have survival and other data for between ~1000 patients from different studies with indications varying from organ transplantation to cancer....

• Replies: 0
• Views: 1,471
06-30-2012, 09:26 AM

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