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# Forum: Biostatistics

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

1. ### How to compare only a part of survival vurves?

My hair got gray now... I have three groups, 3 survival curves ploted, subjects in group 1 & 2 stay around twice as long as in group 3, since the...

• Replies: 6
• Views: 3,206
12-01-2010, 04:05 AM
2. ### Easy question - help asap please?

I have a sample of 23 white women and 25 African American women. In this sample, ten white women smoke, (13 do not) and 3 black women smoke (22 do...

• Replies: 1
• Views: 2,531
12-01-2010, 01:27 AM
3. ### Calculation for Relative Risk for Overweight and Obesity

Please take a look at the following: http://ajph.aphapublications.org/cgi/content-nw/full/94/9/1574/T4 I want to figure out how they calculated...

• Replies: 1
• Views: 4,379
11-28-2010, 06:26 PM
4. ### Qtl anova

Hi, I posted on this site previously but I think maybe the biostatistics section might be more suitable for my problem. It's a genetic data...

• Replies: 0
• Views: 2,479
11-26-2010, 12:52 PM
5. ### log linear model with zero entries

Hi, I have a log linear model with 4 variables (3 dichotom and 1 ordinal). Some (let's say 5 of 2*2*2*4=32) entries are zero. These zeros random...

• Replies: 9
• Views: 8,508
11-25-2010, 04:45 AM
6. ### How to analyze a data set with < & > values?

We are working on vernal pool botany. *There are two types of pool, Natural (control) and Constructed (experiment). Within each pool, over 8...

• Replies: 3
• Views: 4,360
11-24-2010, 02:43 AM
7. ### Need help as a biostatistics moron! Any help appreciated!

Hello I am completely clueless in statistics and I need help for a problem... The problem is about two study groups regarding the lesion size at...

• Replies: 1
• Views: 3,752
11-23-2010, 03:19 AM
8. ### 2-way ANOVA-like analysis with binomial RVs?

Hi, I have a biological dataset and I'm trying to see if certain treatments are correlated with significant changes. In each sample, I'm...

• Replies: 0
• Views: 6,050
11-20-2010, 10:52 PM
9. ### Sampling Question

I work in a hospital setting and I had a researcher ask me a question about sampling for a control group. We are looking at infection rates...

• Replies: 0
• Views: 2,352
noj
11-19-2010, 12:15 PM
10. ### Contingency Table questions

I have a large data set, n=2556. I have two Types, Natural (n=720), Treatment (n=1836) and 3 levels, "Not Present", >0 & <20, and >20. What...

• Replies: 1
• Views: 5,572
11-17-2010, 12:14 AM
11. ### Mixed model in clnical trials using SPSS

Design: 3-arm Randomized controlled trials Group: Treatment 1, Treatment 2, and control Assessment time point: Baseline, End-point, follow-up ...

• Replies: 0
• Views: 4,613
11-15-2010, 07:51 AM
12. ### Comparing screening rates

Hi all, I've been out of school for a bit and am now having anxiety over picking the correct analysis method for a proposal I have to write. I...

• Replies: 0
• Views: 2,845
11-13-2010, 03:44 PM
13. ### Few Questions about P-Value

This is my first post and I had a few questions which I feel I need help. I have read a few textbooks and papers but I am not sure hence. 1. From...

• Replies: 3
• Views: 5,962
11-08-2010, 07:29 PM
14. ### stratified sampled analysis

Hi, I have a data set obteined by a stratified sampling in a cross sectional study. I want to perform logistic regresion analysis however I am...

• Replies: 3
• Views: 2,537
10-29-2010, 05:07 AM
15. ### Parasites in stats

Hi everyone, I am having a bit of trouble in understand the stats that I want to run on an experiment I am doing. Basically I want to do a Chi...

• Replies: 3
• Views: 2,968
10-28-2010, 03:45 PM
16. ### Help in explaining my data, lung cancer- air pollution

Hi, i am doing a ecological study of 402 distrcits from accross the UK to se wether Air pollution effects lung cancer mortalilty (measured in SMR) ...

• Replies: 2
• Views: 3,230
10-25-2010, 11:39 AM
17. ### Cancer survival analysis

If a new treatment appears to improve median overall survival in a group of patients, is there any way to determine whether this improvement results...

• Replies: 3
• Views: 2,844
10-24-2010, 05:55 PM
18. ### Decision Tree

A friend of mine asked me to help him with a decision tree . I found an online calculator and some resource material but I am not sure how to plug...

• Replies: 0
• Views: 3,797
10-23-2010, 12:45 PM
19. ### analysis of the relationship between particulate air pollution and lung cancer

Hi, I am currently doing a study on Lung cancer mortality and air pollution my hypothsis is to see if there is a link. i have 6 variables ( i...

• Replies: 3
• Views: 5,083
10-21-2010, 11:00 AM
20. ### Constant value in logistic regression

Hi, My question concerns the constant represents in logistic regression analysis (which can be included/excluded in SPSS). I am trying to...

• Replies: 3
• Views: 21,667
10-20-2010, 01:03 PM
21. ### standard errors, CIs and logistic regression

A question from a very amateur epidemiologist I am afraid, and a little long winded. I am wondering how to produce the most valid confidence when...

• Replies: 0
• Views: 5,757
10-20-2010, 04:04 AM
22. ### Aggregate trend analysis

Someone I work with said they ran across a paper on a study that contained an analysis which looked at the results of several different outcomes to...

• Replies: 0
• Views: 5,078
10-13-2010, 03:35 PM
23. ### Structure Activity Relationships... LogP, LogD and drug activity

Hi, I am a final year PhD research student and i am assessing novel anti-allergy compounds. I have calculated the LogP (how lipophilic the compounds...

• Replies: 0
• Views: 4,158
10-10-2010, 07:53 AM
24. ### Determining Sample Size

Hi all: I'm having a bit of trouble with the following exercise: You are asked to design a prospective cohort study comparing the risk that...

• Replies: 2
• Views: 5,929
10-08-2010, 06:18 AM
25. ### SNP or Microsatellite?

Hi, My project is to get association between these factors (age, color, gender, and performance) of a particular animal to its genotype. Which...

• Replies: 1
• Views: 2,602
10-08-2010, 06:14 AM
26. ### How to Calculate the Pairwise LD for the given data?

Dear all, I have the following data, which is the output from ms hudson software. segsites: 6 positions: 0.1256 0.3122 0.3218 0.4970 0.5951...

• Replies: 0
• Views: 4,309
10-07-2010, 07:33 PM
27. ### Comparing means problem

Hi, I have run an experiment where I am comparing the temperature required to cause a febrile seizure in several different animal models of...

• Replies: 0
• Views: 2,321
10-06-2010, 11:02 PM

Dear all, this is my first post on this forum with a quick and probably very stupid question. Let's say I have value of a control distribution...

• Replies: 1
• Views: 3,005
10-04-2010, 10:24 AM
29. ### Expected value

I've used Logistic regression to calculate a risk score for death. I've also calculated the probability of dying based on this score. I want to show...

• Replies: 1
• Views: 3,187
10-02-2010, 03:00 AM
30. ### Is my study a case-control or a retrospective cohort study?

Hi All. I'm dipping my toes into medical research and doing an audit of surgical outcomes. I can't work out whether to describe my study as a...

• Replies: 2
• Views: 31,455
09-30-2010, 07:51 PM
31. ### Drowning in data

I'm a GP, and am interested in performing better analysis on patient data. The raw data is around 100mb of data. I am fairly adept by now at...

• Replies: 9
• Views: 4,840
09-28-2010, 05:05 PM
32. ### Cox-regression analysis by using the bootstrap weights

Hi, I am working on a complex survey data set, and I do not have the following variables: Strata and Clusters( because of the confidentiality). On...

• Replies: 1
• Views: 5,419
09-21-2010, 03:53 PM
33. ### Analyzing bovine mastitis with mixed model in SPSS

Hi. I´m a PhD student working in bovine mastitis. I’m trying to analyze a longitudinal study using SPSS version 15. The study consists of 100...

• Replies: 0
• Views: 3,232
09-21-2010, 02:29 PM
34. ### Quasi-Randomized vs. RCT

If a study puts participants in the intervention group based on first come first serve (i.e. the first 65 participants who signed up got the...

• Replies: 5
• Views: 25,347
09-21-2010, 11:54 AM
35. ### Survival tree analysis

I need to perform a survival tree analysis. I have : - 1 independant variable X (numberic variable) - 1 dependant variable Y (overall survival time...

• Replies: 1
• Views: 3,991
09-15-2010, 10:00 AM
36. ### Choosing a distribution with GEE methods

I've just recently been exploring Generalized Estimating Equations for use with my data. I know that QIC values can be used to evaluate which working...

• Replies: 0
• Views: 3,339
09-14-2010, 01:30 PM
37. ### subtract average values with SEM

I have values of two groups, each has its own mean and calculated standad error of the mean (SEM): A +-SEM(A) B +-SEM(B) I wouls like to...

• Replies: 0
• Views: 4,562
09-12-2010, 03:52 AM
38. ### Does cox proportional hazard model control for type 1 error?

I am a greenhorn to survival analysis. Just wondering if there are many covariates, the likelihood that one of them is significant should be quite...

• Replies: 1
• Views: 2,985
09-12-2010, 12:10 AM
39. ### neuronal network analysis - what nethod?

Dear all, I am analyzing the formation of neuronal networks in wild type and transgenic animals. There is very subtle but clear difference in the...

• Replies: 1
• Views: 2,591
09-10-2010, 02:31 PM
40. ### can any body comment on the pros and cons of the research methodology

A Randomized Add-on Trial of an N-methyl-D-aspartate Antagonist in Treatment-Resistant Bipolar Depression Nancy Diazgranados, MD, MS; Lobna Ibrahim,...

• Replies: 3
• Views: 3,821
09-08-2010, 09:46 AM
41. ### Locking a dataset in a stat program

I'm hoping one of the brilliant minds here will be able to help me with this. First some background I'm in the Epi / Biostat field and currently...

• Replies: 4
• Views: 3,652
09-03-2010, 08:34 PM
42. ### Question about R code of survival analysis

I have some questions about cox ph model based on the following demo data set. Thanks a lot for help! > ovarian futime fustat age resid.ds...

• Replies: 0
• Views: 3,615
09-01-2010, 08:10 PM
43. ### Composite Scores/Standardising scores for cognitive outcomes

Hi, I am looking into various methods of combining non-independent cognitive outcome measures on different scales in a clinical trials setting ,...

• Replies: 0
• Views: 6,923
08-31-2010, 12:20 AM
44. ### Interpretation of Odds Ratios

I had a basic query regarding interpretation of Odds Ratio. This particular problem was sent to me by one of my colleagues. The risk factor...

• Replies: 5
• Views: 8,293
08-26-2010, 02:13 AM
45. ### McNemar's test and complex survey data

Hi everyone, I am trying to run McNemar's test on some weighted survey data. I was wondering what changes I have to make to test (if any) to...

• Replies: 0
• Views: 4,185
08-23-2010, 07:13 PM
46. ### Power Calculation- case cotrol study

I am doing a case control study consisting of 1000 controls and 2000 cases. If it was estimated that 21 of about 1000 women were exposed to solvents....

• Replies: 1
• Views: 3,291
08-23-2010, 12:56 PM
47. ### question about a concept

Hey When comparing a diagnositic test (questionnaire) to a reference, let us say for disease and no disease, you could calculate sensitivity and...

• Replies: 0
• Views: 2,230
08-21-2010, 09:32 PM
48. ### confidence interval

if CI of the odds ratio i got was so wide does it have any meaning? and does it make a difference if it contain 1 e.g (0.08- 12) so my...

• Replies: 1
• Views: 2,535
08-19-2010, 06:13 PM
49. ### quick biosci stats question

Hello all, I have a list of patients with their corresponding diagnosis (type of nerve disease) that they received from their primary care provider....

• Replies: 1
• Views: 2,969
08-19-2010, 06:07 PM
50. ### Iguana Analysis

Hello! I am a student currently working on iguana data from an island in the Caribbean close to Cuba (dating 20 years). It is a capture-recapture...

• Replies: 2
• Views: 2,510
08-19-2010, 12:11 AM
51. ### odds and expected B

am doing a cross sectional study, now analysing my data. since my data (the outcome is yes and no) and the independant variables all are catigorical...

• Replies: 0
• Views: 2,587
08-17-2010, 12:29 AM
52. ### confidence interval interpretation (diagnostic tests)

If the 95% confidence interval for a relative risk (RR) or an odds ratio (OR) crosses 1, then this is taken as no evidence of an effect = NO...

• Replies: 2
• Views: 15,935
08-10-2010, 08:40 PM

Dear All, Please kindly help me, if i don't get this done by monday, my ass (job) will be on the line! Anyway, the problem is below: i have...

• Replies: 3
• Views: 3,081
08-09-2010, 07:38 AM
54. ### Sensitivity and specificity of a subset of items

I have a list of 60 stimuli and for each one of them, I have their sensitivity, specificity and ji value for the detection of demented vs....

• Replies: 0
• Views: 2,778
08-08-2010, 12:47 PM
55. ### High power, bias or low power, unbiased?

Assuming we have two estimators and a fixed sample size. One estimator is biased and has high power, the other is unbiased and has low power. Which...

• Replies: 5
• Views: 5,743
08-08-2010, 11:53 AM
56. ### Anova

Hello! I have a problem with data analysis and don't know which method to use. Here is a description of my problem: I have cells that have been...

• Replies: 0
• Views: 1,971
07-27-2010, 07:56 PM

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