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# Forum: Biostatistics

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

1. ### Help on Bhapkar's Test using SAS/R/SPSS?

Hi All, I am currently wandering in the unfamiliar territory of the Bhapkar's test, and hopefully someone can provide some guidance... Please see...

• Replies: 3
• Views: 232
08-22-2016, 09:47 PM
2. ### Help with statistical power?

Hi, I'm doing a study looking at the ability of a test to detect a change in bacterial numbers pre- versus post-treatment . I've done a chi-square...

• Replies: 2
• Views: 121
08-21-2016, 03:01 AM
3. ### Graphpad or SPSS way to analyze this question

Dear friends, I have ~3500 patients. I have ages for everyone of them, and i have a laboratory value for each one as well. I want to know if the...

• Replies: 4
• Views: 187
08-15-2016, 08:48 PM
4. ### Fisher Test for 5x2 table with SAS or R

Hi, I wish to perform a Fisher Test for a 5x2 contingency table. I have a patient population divided in to 5 treatment groups, each with a...

• Replies: 3
• Views: 149
08-13-2016, 11:38 PM
5. ### How to obtain an unbiased post-stratified estimator for survival probabilities?

Suppose I have estimated the survival probabilities $\hat{S(t)}_1, \hat{S(t)}_2, \ldots, \hat{S(t)}_H$ from $H$ strata. Now I want to get an unbiased...

• Replies: 1
• Views: 136
08-13-2016, 09:24 AM
6. ### Help decide on appropriate test for experiment design

Hello - new to the forums here! I work in cell biology and a colleague and I are designing an experiment to determine the appropriate...

• Replies: 1
• Views: 128
08-11-2016, 04:05 PM
7. ### Repeated Measures Analysis with a long baseline period

I am currently attempting to analyze the efficacy of a treatment on a premature baby's SpO2 levels. I have many measurements before the treatment...

• Replies: 0
• Views: 149
08-08-2016, 10:41 AM
8. ### Mean and SD of two means and SD

If we have two groups of males, group 1: age >60 and group 2 <60. each of these groups have mean and SD; can we calculate a mean and SD for all...

• Replies: 13
• Views: 417
08-04-2016, 11:36 PM
9. ### Beginner questions: Clinical trial

Hi there! I am a medical student working on my PhD, and I am analyzing some data for a meeting. Since we don't learn much about statistics (at...

• Replies: 0
• Views: 114
08-03-2016, 02:37 PM
10. ### Interpreting odds ratio in ordinal logistic regression

Hi All, My data is from an educational programme for students. Questionnaire data was collected pre-intervention and post-intervention. We are...

• Replies: 2
• Views: 184
08-03-2016, 01:31 AM
11. ### Is this the right away to perform a trend analysis in a r*c table?

I might be not posting the question in the right forum since I didn't get any advice so far (after 20 viewers) and my project is a public health one,...

• Replies: 1
• Views: 165
08-01-2016, 01:01 PM
12. ### Intrarater reliability for continuous variable

I was hopeful for some advice on how to assess intrarater (not inter) reliability. My specific problem is 1 rater repeats a measurement on 20...

• Replies: 2
• Views: 189
07-30-2016, 12:22 PM
13. ### SAS Coding to find averages for every 60 observations

Hi. I am working on an analysis for research on premature baby health. I ran into a SAS coding issue which I hope some of you can help me with. ...

• Replies: 10
• Views: 255
07-29-2016, 01:38 PM
14. ### Paired or Unpaired T-test?

If I have traps set to capture a certain animal at night vs. during the day, would I use a paired or unpaired T-test? I'd be comparing the mean...

• Replies: 3
• Views: 297
07-28-2016, 03:22 PM
15. ### Cox's regression

Hello, I have some experimental data for animals with tumours. Unfortunately, they were not followed individually during a time course, but...

• Replies: 0
• Views: 182
07-27-2016, 06:03 AM
16. ### starting in biostats and need to analyse clinical data. how to begin.

Hello everybody I am a very beginer in stats and in using SPSS. I need to analyse some clinical data. I want to know please if this is a good...

• Replies: 1
• Views: 255
07-22-2016, 03:54 PM
17. ### Which statistical approach?

Dear all, I am a biologist with a very poor statistical knowledge so please excuse me if my question is not very well formulated- I am doing my best...

• Replies: 4
• Views: 349
07-18-2016, 09:41 AM
18. ### Correct analysis of crossover trials

Hi everybody I was wondering if anyone here had any expertise regarding analysis of crossover trials. I'm writing my thesis at the moment and...

• Replies: 1
• Views: 131
07-18-2016, 08:29 AM
19. ### Author's interpretation of Odds Ratio and Confidence intervals

Hi all, Having some difficulty understanding the results of this paper I am including in a review. It compares the effects of 3 interventions...

• Replies: 1
• Views: 168
07-16-2016, 08:16 AM
20. ### What does a mean probability mean?

Hi all. If each case in a dataset is assigned a probability of a certain event having occurred (based on their own individual data) and I...

• Replies: 1
• Views: 206
07-13-2016, 07:05 PM
21. ### Computing age and gender standardised mean BMI

Hi, I'll appreciate a lot if someone could tell me how to compute age and gender standardised mean BMI in stata. Thanks. ZZ

• Replies: 0
• Views: 305
07-10-2016, 08:20 PM
22. ### Please help interpret cross-sectional study results (odds ratio, relevant risk, etc.)

I'm trying to help my wife with some statistics. She's looking to see if people with Removable Dentures (RD) have a higher prevalence of Combination...

• Replies: 1
• Views: 232
07-09-2016, 03:35 AM
23. ### power calculation for two groups (parallel)

Hi I have got 400 and 600 samples in control and test groups respectively. And in each of these two groups, i have an effect variable that occurs at...

• Replies: 2
• Views: 193
07-08-2016, 10:54 AM
24. ### SPSS, descriptive statistics, crosstabs, risk

the problem has been solved. thanks

• Replies: 0
• Views: 167
07-07-2016, 03:36 AM
25. ### Parallel Bioequivalence Study Sample Size

I need to calculate the required sample size given the following information: Power=80% Coefficient of variation for Cmax and AUC = 40% True...

• Replies: 0
• Views: 255
07-04-2016, 03:26 AM
26. ### How to prove two methods are “similar”?

We are testing two imaging machines. One of the machines has been validated numerous times. However, we built the new machine and we need to prove...

• Replies: 1
• Views: 293
07-01-2016, 10:40 AM
27. ### External Validation of Cox Model

I have two data set (training and validation) for building and validating a Cox model. With the training data set I fitted a cox model using...

• Replies: 8
• Views: 466
06-29-2016, 04:18 AM
28. ### Help interpreting an interaction in Binary Logistic Regression

Firstly, thank you for taking the time to read my problem that I am having. The goal: interpret the direction of the interaction term. ...

• Replies: 3
• Views: 318
06-25-2016, 04:05 PM
29. ### Calculating standard deviation from mean and P value

I am doing a systematic review and one of the papers I am including has reported the data only as mean, sample size and P value. I need the mean and...

• Replies: 10
• Views: 525
CMP
06-24-2016, 10:10 AM
30. ### Permutation correlation with one non-normal variable

Hi, I am trying to assess the relationship between a relatively normally distributed variable (brain volume) and a strongly right-skewed...

• Replies: 1
• Views: 216
06-24-2016, 02:45 AM
31. ### Computing effect size with adverse event counts?

Hello! I'm working on a meta-analysis, and I have a special problem regarding effect size. Can anyone lend me some insight? I have a treatment...

• Replies: 1
• Views: 412
CMP
06-22-2016, 05:34 PM
32. ### Triple crossover study and multivariate model with paired data

Hi, I would like to analyze data from a triple crossover study. Same population received same drug (or placebo) three times a day with...

• Replies: 1
• Views: 359
06-21-2016, 06:50 AM
33. ### Statistical Approach for data (uneven intervals)

Hello, What statistical approach would you recommend for a data of the following pattern. In a 12-hour window, each row/ID is an independent...

• Replies: 0
• Views: 212
rvr
06-20-2016, 12:23 PM
34. ### Test for ordinal DV in mixed design

What's the corresponding test to Two way Mixed ANOVA when the DV is ordinal? I have two treatment groups, 14 time points and the DV is an ordinal...

• Replies: 0
• Views: 543
06-14-2016, 06:55 PM
35. ### Repeatability and Logistic Regression?

Hi all, my stats knowledge is quite basic so I would appreciate any help you can provide! I am working on a study looking at inter-grader and...

• Replies: 2
• Views: 319
06-10-2016, 02:02 PM
36. ### Is this study a case-control or retrospective cohort?

"Recently we retrospectively examined the spine on pyelograms of 34 children with Wilms tumour. The findings were compared with those obtained in 148...

• Replies: 0
• Views: 282
06-02-2016, 11:44 PM
37. ### Significance of a Dichotomous Variable Over a Continuous Variable

Hi all! I ran an analysis using the 2005 healthy eating index (HEI) score as the dependent variable and am a bit confused by my results. The HEI...

• Replies: 1
• Views: 276
06-01-2016, 06:24 AM
38. ### Chi Square for Molecular Screening Comparison

Hi, I'm trying to run a chi square test to compare two different screening methods for a pathogen. I'm testing this by diluting a known positive...

• Replies: 0
• Views: 163
05-31-2016, 03:59 PM
39. ### Best Statistical test for data

Hi All, Just wondering if someone could help with an issue with my data. I am wanting to analyse the relationship between continuous variable...

• Replies: 3
• Views: 387
05-26-2016, 06:49 AM
40. ### ANCOVA assmptions not met.

Hi, What is the non parametric alternative for parametric ANCOVA if we find that some ANCOVA assumptions are not met? How it can be done in SAS?

• Replies: 1
• Views: 191
05-25-2016, 04:03 AM
41. ### Please help me selecting a test for my study

Hi, I was wondering if you guys can provide some ideas on best test for my samples size, since I am not very stat savvy. My project consist of...

• Replies: 4
• Views: 333
05-24-2016, 09:03 AM
42. ### Frequency analysis

Hello. I have a problem with my analysis. I got 2 groups which take drug (Group 1 (50 people) takes real medicine and Group 2 (40 people) takes...

• Replies: 7
• Views: 448
05-23-2016, 08:12 AM
43. ### Non parametric multivariate analysis. maybe :(

Hello to everyone, i need some help with my statistical analysis. I have two different pharmacokinetic parameters. They result from two different...

• Replies: 4
• Views: 408
05-20-2016, 04:07 AM
44. ### Which statistical test shoud I use?

I have concentrations of one metal in two organs of a snail – kidney and foot (n=10). What statistical test should I use to check if the difference...

• Replies: 7
• Views: 358
05-19-2016, 02:27 PM
45. ### LD50 and ED50 calculation with Probit and other methods

hello All i'm not have good experiences in bio-statistic and want to know how can i calculate LD50 for Bacteria and ED50 for Bacterial Vaccine...

• Replies: 0
• Views: 236
05-18-2016, 01:19 PM
46. ### Integrate different types of data from different studies?

Hi, Is it possible to integrate different types of data from different studies? If yes, what precautions we must take? For example, let us...

• Replies: 1
• Views: 249
05-18-2016, 08:26 AM
47. ### Metal accumulation dependence on weight and pollution

I'm working on metal accumulation in two landsnail species and it includes their kidneys and feet. I have concentrations of 7 metals in these organs...

• Replies: 1
• Views: 280
05-18-2016, 07:26 AM
48. ### I do not know how to calculate my sample size…

Hello, can someone help me calculate my sample size and showing me the steps of how it should be done? I am going to do a study to see a...

• Replies: 0
• Views: 270
05-16-2016, 04:37 AM
49. ### Query about RRs and confounders

Hi I am doing my head in over something very simple. Its more theoretical and I'm trying to work out a method. I am hoping someone can clarify...

• Replies: 0
• Views: 205
05-15-2016, 07:02 PM
50. ### Safety or efficacy outcome?

Dear friends, I got confused regarding outcome study I had to review. The primary outcome is: Time to the first occurrence of any of the...

• Replies: 0
• Views: 246
05-14-2016, 12:47 PM
51. ### Problems in Cox proportional hazards model, Survival analysis.

Hello everyone, I got trouble with some problems as following Suppose a Cox proportional hazards model was fit with 2 covariates, smoking status...

• Replies: 1
• Views: 281
05-11-2016, 12:33 AM
52. ### Repeated measures with one between subject and two within subject factors

I have measured plasma cortisol levels in blood samples collected at an interval of 1 hour over a period of 24 hours in 10 male and female animals...

• Replies: 2
• Views: 381
05-08-2016, 08:27 PM
53. ### Best way to calculate power, precision & sample size using complex pilot data set?

I have a large and complex pilot data set of electromyographic (EMG) data collected from human subjects performing several different exercises. A...

• Replies: 2
• Views: 357
05-05-2016, 01:16 PM
54. ### should I include a table with non significant results of Z proportion tests

I am writing a manuscript and have a table with ONLY non significant Z proportion test results. I am wondering whether to omit this table although it...

• Replies: 1
• Views: 237
05-05-2016, 07:26 AM

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