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Threads 1801 to 1860 of 1882

Forum: Biostatistics

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

1. Prevalence rates and prevalence odds ratios

I need to calculate prevalence rates and prevalence odds ratios for a particular disease, classified as 0/1 in my database. In particular, i have to...

• Replies: 0
• Views: 5,344
07-08-2009, 07:02 AM
2. Calculating sensitivity, specificity, etc.of a diagnostic test

I would like to calculate the specifity, sensitivity, positive and negative predictive value etc. for a diagnostic test, possibly with a method that...

• Replies: 1
• Views: 6,973
07-08-2009, 02:08 AM
3. [Help] Logistic regression and goodness-of-fit

Hello. I have a question on "goodness-of-fit" of an ordinal logistic regression run that I did. The results of the ordinal logistic regression...

• Replies: 0
• Views: 4,231
07-04-2009, 11:00 AM
4. likelihood contribution

I have a set of data include survival time, event (1=death; 0=right censored) and treatment (1=yes; 0=no). how to write the likelihood contribution...

• Replies: 0
• Views: 3,792
06-14-2009, 12:30 AM
5. Odds ratios with standardised continuous variables?

Dear TalkStats, I am working on some logistical regression models currently. I understand the interpretation of Odds Ratios, however a friend of...

• Replies: 1
• Views: 7,406
06-10-2009, 02:17 AM
6. Survival Analysis

Has anyone ever done a survival analysis (in medical research) where you first include the treatment variable as the only covariate and then do a...

• Replies: 3
• Views: 4,321
06-02-2009, 10:08 PM
7. Fisher's exact test

Hello, I'm trying to calculate odds ratio and CI of odds ratio for my thesis data using 2-sided Fisher's exact test. I'm using SPSS and everything...

• Replies: 0
• Views: 6,557
05-27-2009, 08:24 PM
8. Difference between Sensitivity and Statistical Power?

Hi, Could anyone point me towards an explanation of the difference between Sensitivity (as described here:...

• Replies: 3
• Views: 13,550
05-18-2009, 11:28 AM
9. regression P value and odds ratios

What does it mean if my P value is significant (.010) but the Odds Ratio is low (.66) Is that even possible? SPSS did the calculation.

• Replies: 1
• Views: 3,934
05-14-2009, 09:01 AM
10. Kaplan-Meier vs Nelson-Aalen

Hi, Working on survival analysis on a bunch of cows that suffer from a common form of disease. I'm trying to get into an analysis pattern here......

• Replies: 0
• Views: 4,675
04-22-2009, 10:49 PM
11. help with decided what tests to use

This study will be a prospective clinical trial to compare the effectiveness of nerve and tendon gliding exercises versus no exercise in a group of...

• Replies: 0
• Views: 1,818
04-16-2009, 08:44 PM
12. Sample Size Calculation

Dear All, How to derive a sample size for the below scenario... To establish "EQUIVALENCE" for two groups provided we are given with both the...

• Replies: 0
• Views: 2,648
04-07-2009, 05:15 AM
13. Calculating life expectancy

I am doing a research project and I need to calculate the life expectancy of a group of musicians. I have a spreadsheet with 400 people and their...

• Replies: 2
• Views: 3,207
03-18-2009, 06:15 PM
14. which test should i use?

Hi, if anybody could help with some Biological statisitics then this would be so great: I'm trying to analyse the significance of some cell culture...

• Replies: 3
• Views: 2,651
03-15-2009, 11:59 PM
15. A doubt in the terminology of sample size calculation

Hi all, While going through a published article of a clinical trial in cervical cancer, I came across this statement under statistical...

• Replies: 0
• Views: 2,224
03-11-2009, 03:59 AM
16. Need some help with a survival analysis

Good Morning! I'm working on a survival analysis involving transplant data. STATUS - graft status TIME - days until graft rejection GROUP -...

• Replies: 0
• Views: 2,411
03-02-2009, 01:31 PM
17. calibration of an existing model

Hi, I would like to assess fitting of a mortality predicting model with original coefficients in another (validation) study population. The...

• Replies: 0
• Views: 2,351
02-27-2009, 04:51 AM
18. Quasi-Randomized trial

Hi there, We are conducting a clinical trial comparing the outcomes of 2 surgical interventions (using 2 different commercial products). Our team...

• Replies: 1
• Views: 9,001
02-21-2009, 06:17 AM
19. Data Format for Repeated Measures AnoVa/SPAnoVa

Hi everyone, I am a newcomer to the forum, SPSS and stats in general. Having followed the inbuilt tutorials in SPSS (V15) and using Julie Pallant's...

• Replies: 5
• Views: 10,138
02-20-2009, 05:35 AM
20. Multicollinearity in binary logistic regression

I have two correlated independent variable and I need to use them both (one as a 'interesting' variable, other one as a control variable). Because of...

• Replies: 10
• Views: 26,883
01-19-2009, 10:03 PM

Hi to everybody, does anybody knows how to calculate Adjusted Odds Ratio when I have a Multiple Logistic Regression model? Do you know about...

• Replies: 1
• Views: 7,477
12-30-2008, 05:09 PM
22. Incorporating time series date into before/after intelligence testing? (n00b alert)

Hello there! A short introduction: My background is pure maths and computer science however I did not take anything past first year statistics at...

• Replies: 1
• Views: 2,273
12-28-2008, 05:14 PM
23. clinical statistics book

Hi, I'm lokking for a book about clinical statistics like this one : 4thEdition Clinical Epidemiology / The essentials / Fletcher & Fletcher ...

• Replies: 1
• Views: 3,393
12-18-2008, 08:56 AM
24. Help me

Dear Sir, My wife is a Post Graduate student of Ophthalmology. We desperately seek your help in the analysis of her desertation work. The objectives...

• Replies: 1
• Views: 2,093
12-15-2008, 10:21 PM
25. HIV-Testing in the desert

Hi, In a lot of popular books about statistics (at least in Germany) there is this example about HIV. Even with a sensitivity of say 99%, the...

• Replies: 1
• Views: 2,944
12-15-2008, 12:40 PM
26. Random Effects Regression vs. Fixed Effects Regression

I'm having trouble distinguishing when to use random effects versus fixed effects regression. Any thoughts?

• Replies: 6
• Views: 35,072
12-10-2008, 08:19 AM
27. Equal Odds

I'm trying to figure out how I can use logistic regression to test the hypothesis of equal odds in a 2 x 2 table of counts? Any ideas? I know I have...

• Replies: 1
• Views: 2,814
12-07-2008, 10:20 PM
28. Is it ok to average ranks?

Dear users, I have a following problem, I have a matrix of results of testing of some chemical substances on a set of various experimental objects....

• Replies: 0
• Views: 2,812
11-26-2008, 03:55 PM
29. Help decide whether I used the right tests

Hi, I have been doing some statistical tests which I'm a little bit out of my depth on for work. The person I'm doing them for knows less than me,...

• Replies: 2
• Views: 3,009
11-19-2008, 05:14 PM
30. One for the pros: conditional logistic regression discrepancy

Ok here´s the problem. I am using R version 2.8.0 on a Windows XP machine. I am not a statistician. I am trying to perform a conditional...

• Replies: 8
• Views: 7,992
11-07-2008, 06:49 AM
31. omnibus test

Hi Is it possible to explain me what's an Omnibus Test ??? I find some definitions on Internet but there is'nt some good concrete example ... ...

• Replies: 4
• Views: 29,175
10-30-2008, 09:00 AM
32. What do YOU mean by "statistically significant"?

Here's a question more about communication than statistical methods. I've experienced that the term "statistically significant" is used often by...

• Replies: 25
• Views: 13,120
10-22-2008, 04:40 PM
33. Help! Data layout and which test?

Hi, :wave: I have some data on a clinical trial. 2 Independent groups, running in paralell, treatment and placebo(n=50). Biological markers...

• Replies: 3
• Views: 3,261
10-14-2008, 08:06 AM
34. Logistic regression with continuous variables

I have levels of eight biochemical markers (continuous variables) and want to determine whether each marker helps to predict the presence or absence...

• Replies: 4
• Views: 11,318
10-07-2008, 05:26 AM
35. Plotting PPV vs. NPV, why?

Hi, I was asked to plot PPV vs NPV, and I'm not sure what such a plot does in general. Is it similar to an ROC curve (sensitivity vs....

• Replies: 0
• Views: 4,388
10-01-2008, 12:51 PM
36. More Repeated Measures Problems!

Hi guys, I have a similar question to johnstephenbyrne. I am analysing the results of a clinical trial. I have measured the levels of a cytokine...

• Replies: 2
• Views: 3,859
09-17-2008, 04:22 PM
37. biostatistical problem--birds and patch size

I have an interesting statistical problem I'm having trouble solving...here's the story: I repeatedly sampled birds along 100m-long transects in...

• Replies: 5
• Views: 3,319
09-17-2008, 07:40 AM
38. Calculating sensitivity and specificity of a *battery* of tests

Hello everyone! I need to calculate the specificity, sensitivity, positive and negative predictive values of a battery of neuropsycholocial...

• Replies: 3
• Views: 6,630
08-30-2008, 05:52 AM
39. diagnostic testing

Medical Testing When evaluating a diagnostic test, one typical constructs a 2 x 2 table and calculates the specificity and sensitivity (true and...

• Replies: 1
• Views: 2,944
08-30-2008, 05:45 AM
40. Clinical Study and Biostatistics

Hy everyone, I have measured a biological parameter in a cohort of 20 patients before they start a therapy (baseline) and then every 2 months for a...

• Replies: 2
• Views: 2,733
08-26-2008, 05:19 AM
41. Repeated measures with censoring

I am conducting an experiment to test spin times of tops. I have 5 aluminum tops and 5 wooden tops. I spin each top 3 times with a maximum spin...

• Replies: 2
• Views: 2,658
08-05-2008, 12:23 PM
42. likelihood ratio for censored data

hi, I'm working on multiply censored data. In order to check which is the law my data follow(weib vs exp), i need to do a test. For the moment,...

• Replies: 1
• Views: 3,864
07-27-2008, 09:35 AM
43. stats for following nominal variables over time??

Hi all, I'm trying to find a method of examining the patterns in symptoms over time. These are only nominal categories. Each patient has...

• Replies: 1
• Views: 2,664
07-17-2008, 03:54 PM
44. Not sure which test to use...

Hi everyone, thanks for reading. I'll try and make this quick, so that hopefully once I know which test I should use I can go and have a go rather...

• Replies: 0
• Views: 2,166
06-08-2008, 08:27 AM

For the data set below, I want to fit a model for log seizure rate, including the main effect of treat and time (as categorical variable with 5...

• Replies: 1
• Views: 3,234
06-01-2008, 05:04 AM
46. I Need help with median and variance...

::wave: hi every1 .. i need help with a biostatistics problem... well it was in spanish so i dont know if i made a good job translating but they are...

• Replies: 1
• Views: 2,445
04-22-2008, 06:23 PM
47. Odds ratio

I am studying risk for cardiovascular disease depending on two different biomarkers. The study -design is a case-control study and I have...

• Replies: 0
• Views: 3,144
04-14-2008, 05:05 AM
48. Which test to use for correlation between groups using ordinal values?

I am trying to test a hypothesis that different decision traps are caused by the same common cause. In the complete picture there are abt 30 decision...

• Replies: 0
• Views: 3,334
04-01-2008, 07:41 AM
49. logistic regression

in logistic regression what does an exp 1 means? that the odds increase or that they remain the same?

• Replies: 1
• Views: 3,734
03-12-2008, 12:14 PM
50. Odds ratios and regression

It's my understanding that odds ratios derived from (multiple) logistic regression is based upon a single unit increase of your variables. If the...

• Replies: 0
• Views: 2,703
02-28-2008, 07:48 AM
51. Relative Impact of Predictors with a Binary Logistic Regress

Hi, I'm trying to find a means to interpret the odds ratios resulting from a binary logistic regression. I have a binary response variable and...

• Replies: 0
• Views: 2,370
02-19-2008, 07:59 PM

I am looking at a database and would need help on what statistical test to use for my research project. There are four groups (for example cars...

• Replies: 2
• Views: 3,994
01-12-2008, 05:57 AM
53. Null Hypothesis for OR

I got this question: "In the background for this study, the authors mentioned that “Data from the Sleep Heart Health Study (Baldwin et al., 2001)...

• Replies: 1
• Views: 3,508
11-28-2007, 07:23 PM
54. EBM Stats

Hi everyone - my first post! Was wondering if anyone could help me. I am doing a project on the outcomes of a particular type of eye surgery...

• Replies: 1
• Views: 2,614
7up
11-25-2007, 12:23 PM
55. Writing a Life Regression Model with Minitab Output

Alrighty, I feel incredibly dumb here so please bear with me. :( I have the following output from minitab from a life regression. Now, what I want...

• Replies: 1
• Views: 3,723
11-15-2007, 10:48 AM

Hi there, Im taking a statistics class online right now because Im going for a degree in Bio technology. When I comes to math I just get so confused...

• Replies: 1
• Views: 8,040
11-12-2007, 11:18 AM
57. LD50 power analysis

Hello all, I come from a biology background, and I wanted to ask a question. We have a value of LD50 (lethal dose), which is the dose at which 50%...

• Replies: 2
• Views: 4,273
11-09-2007, 02:22 PM
58. who can provide good forum about clinical trial data management and biostatistics?

thank you very much!!!多谢大家啦！！！

• Replies: 0
• Views: 5,607
10-29-2007, 11:08 PM
59. Probit Analysis on Limited Data

My problem is how to address data on mortality rates of spiders exposed to three temperatures. I have done probit to analyse similar data with...

• Replies: 4
• Views: 3,884
10-23-2007, 07:11 AM

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