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# Forum: Biostatistics

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

1. ### 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: 1,990
07-27-2010, 07:56 PM
2. ### Odds Ratio vs. P-value

Hi Everyone, I am a Master's student in South Africa investigating genetic susceptibility to tuberculosis. I was running a haplotype analysis and...

• Replies: 2
• Views: 8,729
07-27-2010, 11:08 AM
3. ### 3-group analysis

Hello, I have little project, and today doubts just brought me down. I have sample of 25 patients, and 3 types of disease (a person can have more...

• Replies: 0
• Views: 3,382
07-26-2010, 01:25 PM
4. ### Possible Interaction?

Hi! I've fit the following logistic regression model: Y = waking up with a soar throat (y=1 if yes, y=0 if no) T = type of device (t=1 if type...

• Replies: 2
• Views: 3,098
07-25-2010, 10:22 PM
5. ### odds ratio question

I have the following data: Group A starting in Jan.: Pass: 40, Fail: 60 Group B starting in Feb.: Pass: 90, Fail: 50 Group C starting in...

• Replies: 2
• Views: 2,744
07-25-2010, 09:59 PM
6. ### Outlier

I'd like to ask you a question about some data I have. I have measured the expression of a gene under different conditions. For each condition the...

• Replies: 0
• Views: 3,461
07-25-2010, 07:26 PM
7. ### Question about interactions in regression

So recently, I was told that when using regression with interactions, a main term must always be put in the model. I brought up a situation where I...

• Replies: 2
• Views: 2,680
07-11-2010, 05:54 PM
8. ### Correcting for measurement error in logistic regression?

Hi guys, Myself and a co-author have recently submitted a journal article assessing a particular criminological theory's adequacy in terms of...

• Replies: 5
• Views: 6,294
07-08-2010, 07:15 PM
9. ### censoring provide one example

Hi there, Censored variables come up usually in survival analysis (also in reliability) where the time to event is censored. Thus, usually (or I...

• Replies: 7
• Views: 6,524
07-08-2010, 06:55 AM
10. ### Biometric analysis help

Hello, Im attempting to perform an analysis on a number of characteristics of a subject to identify them. For any given user, I have anywhere...

• Replies: 5
• Views: 3,132
06-23-2010, 09:38 AM
11. ### Help with a molecular biology project

Hello guys I am doing my phd research in molecular biology. I am totally illiterate in statistics that is why i am facing some real problems in my...

• Replies: 3
• Views: 3,689
06-18-2010, 02:08 PM
12. ### Seeking basic analysis help

I have a question regarding an analysis of the number of defects found in products over a certain time period and whether or not a method to fix...

• Replies: 1
• Views: 3,554
06-15-2010, 10:39 AM
13. ### logistic regression model

hello everyone still a newbie in statistics... I made a regression model with binary logistic regression because i have a dichotomous outcome...

• Replies: 2
• Views: 4,271
06-01-2010, 11:06 AM
14. ### Can you calculate the odds ratio for a 2X3 Chi Square?

I know technically you can do the calculation, but what I really want to know is does this give you any statistically relevent information that you...

• Replies: 1
• Views: 10,334
05-15-2010, 06:03 PM
15. ### Need help ...lost, re: clinical research

Hello, First, let me thank you for looking at this post. My question is we are trying to see the effect of X drug on fracture rate. In the...

• Replies: 2
• Views: 3,001
05-10-2010, 09:20 AM
16. ### any Biostatistician around?

Hi, I'm wondering if there's any Biostatistician around in this forum? Looking for a mentor and an ally here. :wave: -anggraini_13

• Replies: 1
• Views: 2,605
05-03-2010, 02:49 AM
17. ### Missing data: Use of the indicator method

Hello everyone, My question pertains to the treatment of missing data and use of the indicator method in regression analyses (i.e. creating either...

• Replies: 0
• Views: 4,675
04-27-2010, 10:59 PM
18. ### Unbalanced Panel data (FEM , REM, or Pooled regression)

Hi, I have unbalanced panel data. Using SAS, the null hypthesis of Hausman Test was not rejected (means the random effects model is better than...

• Replies: 0
• Views: 9,458
04-24-2010, 10:44 AM
19. ### Help with diagnostic test analysis

Hi, I’m doing a project with a physician in a hospital and I am hoping to run some statistics on a data set I have, and I’m realizing now how...

• Replies: 0
• Views: 3,307
04-21-2010, 04:21 PM
20. ### Help interpreting a binary logistic regression

Hi all, I've a question about interpreting the results of a binary logistic regression. I'm using SPSS for my analysis. I've one dependent which...

• Replies: 2
• Views: 5,732
04-20-2010, 09:53 AM
21. ### Interpret the coefficient

In a study of melanoma, survival times in months were obtained for 214 patients. The following potential explanatory variables were considered: sex...

• Replies: 0
• Views: 4,793
04-07-2010, 09:56 AM
22. ### Power calculations help..

Hello all, I don't suppose i can ask a question on power calculations? I've just conducted a RCT involving two student groups one undertaking...

• Replies: 4
• Views: 5,558
03-30-2010, 09:39 PM
23. ### Strengths of mixed model

Hello forum, I am doing a clinical trial with crossover design and repeated measurements. (4 treatment groups and 11 subjects.) I have been...

• Replies: 0
• Views: 3,010
03-25-2010, 08:21 AM
24. ### Bacterial death rate statistics - I need help!

My masters dissertation focusses on bacterial survival time on paper surfaces, using E.coli and S.aureus When plotting log cell count against time...

• Replies: 2
• Views: 3,963
03-24-2010, 07:09 PM
25. ### Help with GLM/logit diagnostics and result interpretation

I have this complex toy example trough which I'm trying to learn how I can apply generalized linear models (a logit model to be exact where the...

• Replies: 3
• Views: 7,224
03-23-2010, 12:24 AM
26. ### Positive predictive value

I've conducted an experiment where I calculated a positive predicted value, what statistical test can I use to assess these values?

• Replies: 1
• Views: 5,809
03-17-2010, 05:43 AM
27. ### Statistical test for sensitivity and specificity

Hi everyone, I'll make this as quick and easy as possible :) I've carried out a project where I compare the efficiency of two tests used for the...

• Replies: 2
• Views: 7,061
03-16-2010, 01:52 AM
28. ### How to make a heatmap in R for a microarray data?

Hi guys, I have been given a microarray data for which I need to figure out a heatmap. Unfortunately I have never had a chance and experience in...

• Replies: 2
• Views: 13,053
03-08-2010, 03:16 PM
29. ### Odds Ratio and Confidence interval for McNemar's Test

How would you calculated the odds ratio and confidence intervals for a McNemars test applied to a 2 × 2 contingency table on matched, case controled...

• Replies: 0
• Views: 5,695
03-08-2010, 12:15 PM
30. ### Survival time of components - what approach

Hey, Some electronic components have had their time to breakdown x, recorded. During manufacturing they have been hardened for different amounts...

• Replies: 0
• Views: 2,746
02-28-2010, 01:20 PM
31. ### Confidence Intervals / Chi Square Methodology

I'm working on a project for school and I need some help determining how to best understand the following situation (any help is greatly...

• Replies: 2
• Views: 3,045
02-22-2010, 07:28 AM
32. ### G*Power Apriori Power Calculation

I am wanting to do a power calculation using G*Power. I want to know the sample size when I am intending to do some Multinominal Logistic Regression...

• Replies: 0
• Views: 6,691
02-16-2010, 06:04 PM
33. ### Logistic regression

Hi, I am stuck with my assignment question for awhile, need some advise on solving. Here is the question: The following logistic model (Model A)...

• Replies: 4
• Views: 3,571
02-11-2010, 03:09 AM
34. ### P values in Medical Writing

My apology for this simple question but it's one I have run into before and would like some assistance with. The following was posted on a medical...

• Replies: 3
• Views: 6,838
02-10-2010, 10:58 AM
35. ### interpreting logistic regression

I am having a tough time interpreting output in terms of what the coefficients and odds ratio say about the estimated effect. For example, say you...

• Replies: 1
• Views: 5,152
01-31-2010, 07:57 AM
36. ### Survival Analysis

Just a quick question on running a survival analysis. Regarding the Time to Event variable, how is it coded? For example, if I'm measuring...

• Replies: 4
• Views: 4,201
01-27-2010, 08:21 AM
37. ### Contingency Tables/Chi Square Test

Hi all, Please help statistics gurus! I've searched through some of the postings but couldn't find the specific answer I was looking for. If I...

• Replies: 2
• Views: 3,538
01-10-2010, 06:19 PM
38. ### Ancova

Hi, I have a question regarding ANCOVA. I feel it might be a stupid one but there you go. I have 2 groups (men and women) for which I am scoring a...

• Replies: 1
• Views: 2,749
01-08-2010, 12:23 PM
39. ### ROC curve from logisitc regression Bootstrap analysis in Stata 9.2

Hello, I am doing an analysis to predict an outcome (death) from a database. The model is suposed to be used to predict which children need immediate...

• Replies: 5
• Views: 9,364
12-18-2009, 03:27 PM
40. ### power analysis

dear friends hi! i am relatively new in the site so plz forgive any errors of me!! i have this problem: i am doing a case control study, trying to...

• Replies: 0
• Views: 2,771
12-11-2009, 01:10 PM
41. ### Logistic Regression (Odds Ratio)

Hi, Question: In terms of the risk reduction as conveyed by the odds ratio, one year of age corresponds to how many pounds of initial weight? Is...

• Replies: 0
• Views: 3,904
12-04-2009, 08:12 AM
42. ### logistic regression interaction term - change between main effects and full model

Hello, I would appreciate your help with this problem. I have a binary logistic regression model. The main effects model includes female (coded...

• Replies: 0
• Views: 5,689
12-01-2009, 03:32 PM
43. ### What implications does the relationship between sensitivity/sentificity have?

It's the last question in my assignment. I have already worked out that the sensitivity and specificity of a test go in opposite directions depending...

• Replies: 0
• Views: 2,240
11-26-2009, 04:43 PM
44. ### Logistic Regression Help

I am having difficulty interpreting the significance of this output: Attainment and still enrolled (Dependent variable) Time the job executed...

• Replies: 3
• Views: 3,519
10-24-2009, 05:57 PM
45. ### logistic regression intercept is negative and not significant

Hi, I have a logistic regression question. My dependent variable is coded 0, 1. When I run my models, the intercept (constant) is negative, and...

• Replies: 3
• Views: 20,332
10-23-2009, 11:52 AM
46. ### Ordinal Regression or Probit Analysis?

Hi Guys, I am currently researching the survival rates of hedge funds. I am trying to find the effect of certain fund characteristics (risk,...

• Replies: 0
• Views: 3,762
09-27-2009, 10:45 AM
47. ### Determining the probability that a sample is accurate

I recently read an article concerning a new HIV vaccine developed in Thailand. The article can be found here...

• Replies: 1
• Views: 3,437
09-25-2009, 08:12 PM
48. ### Calculating sensitivity SS and specificity SP from the SS&SP of subitems

Hello everyone, so here is a question for you. I have a table of 60 test items that were evaluated in both controls and patients, each item has &#37;...

• Replies: 0
• Views: 4,045
09-21-2009, 08:13 AM
49. ### weighted standard error of the mean

Hi, I am trying to calculate some statistical properties pertaining to mobility of cargo inside cells for my research, but due to my poor...

• Replies: 1
• Views: 13,984
09-13-2009, 07:19 AM
50. ### Confidence Level of a Sorting Method?

We recently had an issue in production. I had come up with a test method that seemed capable of sorting the bad product out from the good product....

• Replies: 0
• Views: 3,596
09-11-2009, 03:10 PM
51. ### GLM with binomial errors: underestimating interactions?

I have problems with analyzing survival data, from experiments in a 2x2 factorial setting - the statistical approach which I am using seems to...

• Replies: 3
• Views: 3,793
09-01-2009, 07:14 AM
52. ### Extreme right skewed data and repeated measures

Hi! I’m writing for the first time and I would be grateful if someone could help me. I am total statistics beginner and additionally I’m a doctor so...

• Replies: 7
• Views: 6,092
08-22-2009, 07:44 PM
53. ### odds ratio in Fisher's exact test?

Hi, I ran a fisher's exact test in SAS, in the output they show you the odds ratio and relative risk estimates. Can I use these estimates to...

• Replies: 1
• Views: 4,643
08-01-2009, 10:18 AM
54. ### How to interpret hazard ratio for continuous variable

Hi, I'm looking at survival curves for some data and wanting to see the effect of covariates in a Cox proportion hazards model, but am new to this...

• Replies: 0
• Views: 8,796
07-09-2009, 10:25 PM

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