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# Forum: Biostatistics

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

1. ### help- comparison of 2 groupes of categorical data‏

Dear all, I may need your suggestion for a statistical question. Now I have 2 groupes of data, I wanna see if there are differences in the...

• Replies: 6
• Views: 239,258
02-15-2011, 10:28 AM
2. ### 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: 60,517
08-17-2012, 07:50 AM
3. ### p value of 0.000 on SPSS

I am using SPSS to define relationship between two variables. Previous research has indicated a significant relationship between them. Spearman...

• Replies: 6
• Views: 58,930
03-10-2013, 03:16 PM
4. ### Sample Size for Chi Square test

Hello, I need to calculate a minimum sample size for the chi square test. I have two groups, sick and healthy patients, and I have a new test...

• Replies: 7
• Views: 39,030
01-05-2012, 06:49 AM
5. ### Odds ratios less than 1, how to make interpretation ?

Hello all, How do I make interpretation of odds ratio equal to 0.02, given from a logistic model with a binary outcome and let's say 2 treatments...

• Replies: 5
• Views: 36,855
04-28-2013, 12:33 AM
6. ### 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: 35,296
12-10-2008, 08:19 AM
7. ### Is Fríedman one-way or two-way ANOVA test by ranks?

Hi, Friedman test is frequently called a one-way or two-way analysis of repeared measure ANOVA on ranks. But what is it, similar to one-way or...

• Replies: 2
• Views: 33,680
10-15-2012, 12:46 AM
8. ### Interpretation of Relative risk and confidence interval?

There were fewer primary events in patients assigned to warfarin than in those assigned to aspirin (24, 1·8% per year vs 48, 3·8% per year, RR 0·48,...

• Replies: 8
• Views: 33,673
04-01-2011, 02:10 AM
9. ### 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: 32,156
09-30-2010, 07:51 PM
10. ### 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: 29,813
10-30-2008, 09:00 AM
11. ### STATA or SAS? Which one should I learn?

Hello I am currently trying to go a little beyond SPSS by learning either SAS or STATA. My field is psychology and biostatistics. Which one of these...

• Replies: 17
• Views: 28,161
03-11-2014, 11:50 AM
12. ### cox regression v. kaplan-meier

hi everyone! thanks in advance for your help! i'm studying whether the presence of high v. low hormone levels (of several different hormones)...

• Replies: 4
• Views: 27,519
04-26-2012, 10:41 AM
13. ### Two sample Kolmogorov–Smirnov test

I would like compare our ideal sample distribution to that from other samples in a study examining the age at onset (AAO) in schizophrenia, which is...

• Replies: 2
• Views: 27,514
10-19-2012, 10:51 AM
14. ### 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: 27,465
01-19-2009, 10:03 PM
15. ### 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: 26,850
09-21-2010, 11:54 AM
16. ### 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: 22,849
10-20-2010, 01:03 PM
17. ### Can a cohort study have no control groups (is a clinical series study a cohort)?

Hi AFAK a cohort study needs a matched control group. However, its definition doesn't necessitate a control group. Moreover, I have read some...

• Replies: 5
• Views: 22,778
06-22-2011, 11:45 PM
18. ### Determining significant (or otherwise) difference between 2 rates of change

Dear Users, I am trying to determine the statistical significant difference (or otherwise) between 2 series of data and am unsure how to proceed....

• Replies: 7
• Views: 22,519
01-09-2012, 02:21 AM
19. ### 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: 21,030
10-23-2009, 11:52 AM
20. ### comparing multiple sequences of data over time

Hi, would really appreciate help on how to test my data! I've three groups (with 5-8 individuals in each group; actually 5 in one and 8 in each of...

• Replies: 4
• Views: 20,156
06-07-2011, 11:47 AM
21. ### wilcoxon rank sum test or t-test?

Hello, I have a question for my analysis and reporting. For my analysis, simply said I measured the time needed to achieve sufficient pain...

• Replies: 8
• Views: 20,021
08-07-2011, 07:04 AM
22. ### 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: 19,537
08-19-2012, 12:55 PM
23. ### Power analysis for non parametric tests (sample calculation)

Hi, I am preparing a little presentation on power calculation for parametric tests and it occured to me that I don't know how it works for...

• Replies: 2
• Views: 18,969
10-24-2012, 10:07 AM
24. ### Any statisticians out here please? £50 voucher offer

I am doing a survey as part of my MSc project and need someone to review the protocol from a stats point of view, including helping to determine the...

• Replies: 23
• Views: 16,648
12-15-2014, 06:28 PM
25. ### 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: 16,329
08-10-2010, 08:40 PM
26. ### Should I use Tukey-Kramer or Fisher's LSD post hoc test to follow up my 1-Way ANOVA?

Dear forum members, As part of a wildlife monitoring study, I ran 1-Way ANOVAs, where the Fixed Factor has three treatments: n1=5, n2=6, n3=5. I...

• Replies: 3
• Views: 16,098
12-15-2012, 01:23 PM
27. ### Should I use an ANCOVA or two t-tests?

Hi I'm studying the level of an ion in patients compared with matched controls. My results are categorized by gender and cohort/control...

• Replies: 10
• Views: 14,871
10-04-2011, 01:41 PM
28. ### 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: 14,248
05-18-2009, 11:28 AM
29. ### 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: 14,247
09-13-2009, 07:19 AM
30. ### 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: 13,524
10-22-2008, 04:40 PM
31. ### 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: 13,421
03-08-2010, 03:16 PM
32. ### equal or unequal sample size ?

I have a simple theoretical question... Let's say I have a sample of 30 subjects from group A and 150 from group B, and I want to run a t-test. ...

• Replies: 6
• Views: 12,914
02-15-2012, 09:06 AM
33. ### best biostatistics textbook?

I have Health and Numbers. I'd like to get another book to supplement. Recommendations? Looking for clear and simple! Thanks!

• Replies: 3
• Views: 12,697
10-05-2005, 11:26 PM
34. ### Mann-Whitney U and Bonferroni Correction

I recently presented some work in my department in which my colleagues and I had applied a Mann-Whitney U test for multiple pairwise comparisons. We...

• Replies: 3
• Views: 12,626
04-08-2013, 09:31 AM
35. ### Is my study case-control or retrospective cohort?

Hi AFAIK if we split the sample by the exposure, it is retrospective cohort; and if we split it by the disease, it is case control. I am...

• Replies: 8
• Views: 12,479
05-13-2011, 11:18 AM
36. ### Clinical Significant vs Statistical Significant

Hi Guys, I read some strong criticism about "statistical significance". Some researchers claim that statistical significance is useless. in...

• Replies: 8
• Views: 12,255
07-25-2011, 12:43 PM
37. ### How to adjust data of confounding variables adjusting diabetes to BMI and age

I am doing a study of pregnant diabetes women. There are 3 types Type 1 , 2 and gestational. Then various ages and bmis. Outcomes study include type...

• Replies: 6
• Views: 11,783
02-22-2012, 08:41 AM
38. ### Test for linear trend in odds ratio in linear regression

I often see epidemiological studies where a continuous variable has been divided into quantiles and the odds ratios for each quantile compared with a...

• Replies: 10
• Views: 11,727
09-04-2015, 01:16 PM
39. ### 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: 11,574
10-07-2008, 05:26 AM
40. ### Concordance index in survival analysis (cox regression) adjusted for competing risk

Hello everybody! First of all this is truely a wonderful place for discussion about statistics. I have been looking here from time to time and I...

• Replies: 3
• Views: 11,368
01-17-2012, 12:37 PM
41. ### Interpreting Cox proportional hazards regression p values

Hi guys, I have been testing the hypothesis for difference of survival between four different classes by using coxph function of survival package...

• Replies: 2
• Views: 10,844
02-16-2011, 05:35 AM
42. ### 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: 10,704
05-15-2010, 06:03 PM
43. ### Multiple Ailments

1 in 24 people in the US are diagnosed with COPD, 1/314 with Parkinsons, 1 in 12 with heart disease. What is the chances for a person to have a 3...

• Replies: 5
• Views: 10,602
08-31-2013, 04:33 PM
44. ### data analysis for retrospective cohort study

Hi!! Im embarrassed to be asking v basic questions :o I proposed a study topic for my group assignment, looking at cancer rates between...

• Replies: 2
• Views: 10,545
04-09-2011, 06:13 AM
45. ### diagnostic testing and sample size calculation

Hello everyone, I did a study evaluating 2 screening tools (questionnaires) compared to a reference in the same sample of patients. So all the...

• Replies: 4
• Views: 10,412
05-31-2012, 06:22 PM
46. ### 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: 10,411
02-20-2009, 05:35 AM
47. ### General two-way ANOVA questions

Hi, I have the following factors in my data: pretreatment (yes or no), drug_dose (1, 2, 3, 4) and neurochemical levels (dependent variable). ...

• Replies: 4
• Views: 10,379
12-21-2010, 03:16 AM
48. ### How to do post hoc tests in logistic regression?

I looked at whether participants recycled after being subjected to a given message. There were three groups: a Control group, group A, and group B. ...

• Replies: 2
• Views: 10,264
04-01-2012, 07:40 PM
49. ### Repeated measure analysis using SAS (crossover design)

I joined the forum in desperation as I urgently need help and I hope there is somebody out there that will be able to help me.:shakehead Some...

• Replies: 1
• Views: 10,263
09-25-2011, 08:46 PM
50. ### Likelihood ratio in Cox regression analysis?

I have done a great deal of research without any success regarding the interpretation of likelihood ratio (LR) test in Cox regression analysis. If...

• Replies: 1
• Views: 10,119
11-19-2012, 06:01 PM

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