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Forum: Biostatistics

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

  1. How to calculate the confidence interval of the ratio of two means (paired data)

    Hi there, I am writing a systematic review and need to calculate the 95% confidence intervals of the ratio of means from whatever the clinical...

    Started by FitzChivalry‎, 02-18-2015 05:17 PM
    confidence intervals, paired data, ratio of means
    • Replies: 7
    • Views: 281
    Today, 04:06 PM Go to last post
  2. Regression vs. t-test

    Hello all, I have this small study, and I am wondering how to analyze it. I have a measure X taken before some event, and after for every...

    Started by Yankel‎, Today 05:52 AM
    • Replies: 6
    • Views: 122
    Today, 02:53 PM Go to last post
  3. Is the Cox Model correct in this case?

    Dear all, thanks for the help in advance, this is my issue: I am studying whether skipping a scheduled medical examination (which is every 4 weeks...

    Started by Ralph84‎, Today 01:27 PM
    • Replies: 0
    • Views: 35
    Today, 01:27 PM Go to last post
  4. Survival curve from competing risk analysis

    I conducted a competing risk analysis of time-to-event data and produced graphs for the cumulative incidence functions. The investigator that I am...

    Started by mostater‎, Today 10:07 AM
    • Replies: 1
    • Views: 38
    Today, 12:58 PM Go to last post
  5. Question Need help

    I have 3 groups, out of these 3, 1 is the control group. other two i have studied the effect of two modes of exercise. so i have before and after...

    Started by pavithran‎, 02-27-2015 10:25 AM
    • Replies: 2
    • Views: 161
    Today, 12:28 PM Go to last post
  6. Linear Mixed Model Analysis with multiple fixed factors

    Hellow, Here is a question on linear mixed model analysis for an intervention The study composed of two group of subjects who receive a DrugA...

    Started by risu‎, 02-20-2015 06:09 AM
    • Replies: 2
    • Views: 162
    Today, 12:14 PM Go to last post
  7. Case control study - selection of control group

    I am starting a nested case control study using a pre existing dataset. I want to look at patient factors associated with relapse of tuberculosis. I...

    Started by andros23‎, 01-07-2015 11:12 AM
    case control; matched, stata commands
    • Replies: 5
    • Views: 322
    03-02-2015, 11:08 AM Go to last post
  8. comparing two dose(inhibition) respose curves log vs log log

    I'm not a stats person, so I need some help. I am looking for a statistics model to compare one dose(inhibition) response curve to the log space...

    Started by BrainExploding‎, 02-27-2015 04:52 PM
    • Replies: 0
    • Views: 93
    02-27-2015, 04:52 PM Go to last post
  9. Clustering sites to compare with cluster of species similarity (dendrogram?)

    Hi, I hope someone can help me here. I kind of have something specific in mind to analyze parts of my data, but I am not sure how to get there. I...

    Started by Aquaziell‎, 02-20-2015 10:35 AM
    • Replies: 2
    • Views: 166
    02-27-2015, 01:06 PM Go to last post
  10. Calculating life expectancy for cancer patients

    Hi all I have been asked to use life table analysis to calculate life expectancy for cancer patients from birth. I am comparing 3 different...

    Started by Suze‎, 02-26-2015 03:56 AM
    life expectancy, survival analysis
    • Replies: 0
    • Views: 71
    02-26-2015, 03:56 AM Go to last post
  11. How to calculate the covariance of two paired, continuous measurements

    Hi there, Is it possible to calculate the covariance of two paired, continuous measurements in a before-after clinical trial design without the...

    Started by FitzChivalry‎, 02-25-2015 11:43 PM
    • Replies: 0
    • Views: 91
    02-25-2015, 11:43 PM Go to last post
  12. Retrospective review analysis questions

    Hello! I am new to this forum. Thank you in advance for any help you can give!:wave: I am doing a prelim analysis for a pilot study I have...

    Started by boomer‎, 02-25-2015 10:57 AM
    • Replies: 3
    • Views: 148
    02-25-2015, 05:46 PM Go to last post
  13. outcomes of surgery

    Can someone point me into the right direction I have a database of patients who have had surgery which is deemed a success or not(0,1). Each...

    Started by edmundfitz‎, 02-23-2015 05:32 PM
    logistic regression
    • Replies: 3
    • Views: 182
    02-24-2015, 03:47 PM Go to last post
  14. Chi square vs Mcneamar's test

    Hello I have a cohort study where a cohort of subjects with a specific characteristic has been matched to a control group according to age (+/ 3...

    Started by Ralph84‎, 02-14-2015 09:56 AM
    • Replies: 3
    • Views: 261
    02-23-2015, 11:43 AM Go to last post
  15. [R] Non-parametric test to multi factorial ANOVA

    Hi, I've spent hours searching online (by "non parametric factorial ANOVA"), reading in books (Zar's "Biostatistical analysis") and manuals (R),...

    Started by Saccharo‎, 02-19-2015 06:52 PM
    • Replies: 3
    • Views: 244
    02-23-2015, 10:19 AM Go to last post
  16. Formula for S shaped curve given specific values

    I need to derive a formula that will give me an S-shaped curve, such as this one: The x-values would go from 0 to 250 and the y-values from 0 to...

    Started by Sharidb‎, 02-19-2015 05:54 AM
    gompertz, logistic
    • Replies: 3
    • Views: 154
    02-19-2015, 01:52 PM Go to last post
  17. Pearson's versus Spearman's correlation

    I am trying to determine which correlation coefficient is more appropriate. The two variables to be correlated are visual acuity (which can be...

    Started by jle‎, 02-11-2015 07:54 PM
    • Replies: 6
    • Views: 351
    02-13-2015, 05:59 PM Go to last post
  18. Sample size calculation in clinical trial

    Could you please help me understand how did they calculate the sample size in this randomized trial ? It is a randomized trial comparing the use...

    Started by goodfella‎, 02-12-2015 11:29 AM
    • Replies: 0
    • Views: 126
    02-12-2015, 11:29 AM Go to last post
  19. Cmax as covariate in mixed model?

    Hello, I am involved in a study looking at drug effects on HR. We have one treatment and one placebo group, and are testing patients once/week for 8...

    Started by jcr‎, 02-11-2015 10:08 PM
    • Replies: 0
    • Views: 92
    02-11-2015, 10:08 PM Go to last post
  20. Comparison of two variables from one sample set

    I have collected two measurements from a set of 100 tumour biopsies. One measurement is the percentage mutant allele of a particular mutation. The...

    Started by p_a_c‎, 02-11-2015 11:18 AM
    • Replies: 2
    • Views: 152
    02-11-2015, 03:49 PM Go to last post
  21. Which test/study to use?

    Hey Guys, I was wondering if I could get some help. Lets say you have a group of patients who are positive for a disease based on the gold...

    Started by robnon‎, 02-09-2015 03:48 PM
    • Replies: 6
    • Views: 264
    02-10-2015, 03:48 PM Go to last post
  22. How many people have the disease based on the prevalence?

    Hi, I know that Prevalence=(persons with a given health indicator during a specified time period/ population during the same time period) X...

    Started by alanend‎, 02-10-2015 11:14 AM
    • Replies: 4
    • Views: 118
    02-10-2015, 12:19 PM Go to last post
  23. Trouble writing results

    I have a lot of trouble writing up results in text. At present I have a one table which has descriptive statistics and univariate analyses (i.e....

    Started by jle‎, 02-10-2015 12:55 AM
    • Replies: 0
    • Views: 121
    02-10-2015, 12:55 AM Go to last post
  24. One-Way ANOVA and tongue testing

    I have a pretty basic question about using a one-way ANOVA. I am performing an oral tribology experiment on pig tongues which basically means I am...

    Started by oomchu‎, 02-05-2015 02:19 PM
    anova, conditions, one-way
    • Replies: 2
    • Views: 246
    02-06-2015, 02:07 PM Go to last post
  25. comparing results of 2 chi2 tests, + proper graphing

    Hello, i was wondering what the appropriate test would be for comparing the results of 2 chi square tests. For example, if I did one experiment...

    Started by statsnewby‎, 02-06-2015 01:48 PM
    chi2, graph menu
    • Replies: 0
    • Views: 131
    02-06-2015, 01:48 PM Go to last post
  26. Test validity

    Hello friends, I'm really new at this, I'm in high school, and wanted your help to know how does someone check or calculate if a test is actually...

    Started by Pammy‎, 02-03-2015 04:15 AM
    • Replies: 10
    • Views: 340
    02-05-2015, 01:13 AM Go to last post
  27. Calculating & Interpreting Cohen's D Effect Size

    Dear all, Im new to effect size & am struggling with some of the calculations, hence would like to seek some thoughts / advice. 1) Im calculating...

    Started by zeroX14‎, 02-02-2015 11:39 PM
    • Replies: 12
    • Views: 375
    02-04-2015, 06:58 PM Go to last post
  28. What statistical test to use ?

    For example :- I have a drug of two different doses (low dose and High dose) and i want to test this drug of two different doses on 3 age groups of...

    Started by mattmatt0099‎, 02-03-2015 08:37 AM
    • Replies: 2
    • Views: 169
    02-03-2015, 12:04 PM Go to last post
  29. Really new at this - need help

    Hello friend, I al 18 years old and taking a bio stat class. I have never taken stats and I;m really poor in math. Could someone help break...

    Started by Pammy‎, 01-20-2015 07:18 AM
    • Replies: 4
    • Views: 213
    02-03-2015, 03:55 AM Go to last post
  30. Permanova using adonis, comparing a focus group with the rest (all other groups)

    Dear all I would like to compare the community composition of a certain region, against the composition of the neighbouring regions. This is an...

    Started by Aramara‎, 02-03-2015 02:27 AM
    adonis, different groups, permanova, r program
    • Replies: 0
    • Views: 118
    02-03-2015, 02:27 AM Go to last post
  31. Confidence intervals: normal vs t-distribution (central limit theorem)

    Hi all! We did a serological survey for a disease taking 300 samples in a population of 50 000. If our sample mean gives a 2% prevalence. How...

    Started by Johann Kotze‎, 02-01-2015 02:54 PM
    central limit theorem, confidence intervals
    • Replies: 2
    • Views: 218
    02-02-2015, 09:40 AM Go to last post
  32. IRR over time for different areas?

    Hi all, I'm not quite sure why I'm getting confused about this, but I am! So I have 3 different areas and my study period is over 17 years with...

    Started by wernie07‎, 02-01-2015 10:59 PM
    • Replies: 0
    • Views: 131
    02-01-2015, 10:59 PM Go to last post
  33. Vitamin D deficiency & disease outcomes - assistance with interpretation of SPSS res

    Hello everybody! As part of my diploma work on the effects of vitamin D deficiency I'm incorporating results from a cross-sectional survey on a...

    Started by gaggantas33‎, 01-20-2015 10:06 AM
    • Replies: 2
    • Views: 249
    01-30-2015, 04:04 AM Go to last post
  34. getting in deep..

    Hello, I am attempting to do statistical analysis on data that I've collected, but I am starting to feel overwhelmed by the choices as I read...

    Started by rocketmotor‎, 01-29-2015 11:11 PM
    • Replies: 1
    • Views: 160
    01-30-2015, 03:53 AM Go to last post
  35. P-values with confidence intervals - where do they come from?

    Below is quoted a part of my comments in reviewing a scientific paper. I'm not a statistician so I want to make sure I'm not missing something. Do...

    Started by Johann Kotze‎, 01-29-2015 03:14 PM
    • Replies: 2
    • Views: 174
    01-30-2015, 03:46 AM Go to last post
  36. regression with covariates having "structural" zeros in contingency table

    Hello. I'm examining associations of various risk behaviors within a clinical cohort on having a suppressed or un-suppressed HIV viral load using...

    Started by psacamano‎, 01-29-2015 05:58 PM
    • Replies: 0
    • Views: 126
    01-29-2015, 05:58 PM Go to last post
  37. help calculating needed sample size

    hi im conducting a study on a certain ratio in a blood exam (lets call it X) . I aim to say that there is a certain sensitivity (let say>80%) for...

    Started by urilee‎, 01-25-2015 04:18 AM
    • Replies: 1
    • Views: 266
    01-28-2015, 05:43 PM Go to last post
  38. Multiple Imputation in R on variable with repeated measurements

    Hello! I am working with an occupation cohort exposed to radiation and have a dataset containing a number of variables on each worker, including...

    Started by PamD‎, 01-22-2015 03:12 PM
    • Replies: 0
    • Views: 211
    01-22-2015, 03:12 PM Go to last post
  39. Median follow Up shorter than median over all survival, possible?

    Hello, I calculated overall survival and median follow up with Kaplan Meyer. In particular follow up was calculated as inverse of overall...

    Started by greeklatin‎, 01-22-2015 09:04 AM
    • Replies: 2
    • Views: 155
    01-22-2015, 11:15 AM Go to last post
  40. Project Issue.

    I am a student of statistics discipline. I have to conduct a project which i can apply in society or nation. My preferable topics are...

    Started by Cynderella‎, 01-22-2015 04:55 AM
    applied statistics, biostatistics, project, research for thesis, self-study
    • Replies: 0
    • Views: 165
    01-22-2015, 04:55 AM Go to last post
  41. Which test to use?

    Hello guys, I am conducting a study to evaluate the effect of supplementation on serum vitamin levels. There are four categories based on the...

    Started by bsing82‎, 01-20-2015 01:48 AM
    • Replies: 5
    • Views: 300
    01-21-2015, 04:49 AM Go to last post
  42. Determining seasonal sample size

    I intend to deploy a new sonar system at our weir to help us count migrating fish. This new system cannot identify gender. We have six years of...

    Started by KellyD‎, 01-20-2015 04:07 PM
    • Replies: 0
    • Views: 163
    01-20-2015, 04:07 PM Go to last post
  43. Help finding appropriate test when observations are non-independent

    I have a data set consisting of data from 7 islands. I have measured the average gene flow between each pair of islands as well as the difference in...

    Started by mlogan1983‎, 01-20-2015 12:23 PM
    biostatistics, correlation, independence, non parametric, pairwise comparisons
    • Replies: 0
    • Views: 118
    01-20-2015, 12:23 PM Go to last post
  44. Struggling with this power/effect size analysis, any help?

    Hello all, I am trying to calculate the effect size or power analysis for this study to assess my probability to detect a phenomenon/change, here are...

    Started by Ralph84‎, 01-20-2015 06:40 AM
    • Replies: 0
    • Views: 132
    01-20-2015, 06:40 AM Go to last post
  45. Question Ecology: how to compare "intrinsic growth rates" (r)

    Hi everybody, I would like to know how to statistically compare different "intrinsic growth rates", most of the times named "r", belonging to...

    Started by Reset85‎, 01-19-2015 11:13 AM
    ecology, ecotoxicology, euler-lotka, intrinsic growth rate, toxicology
    • Replies: 0
    • Views: 145
    01-19-2015, 11:13 AM Go to last post
  46. Locating significantly different data points in a sample

    Hi, I have question regarding some data I collected recently which can be represented as plain integers (basically the number of features (dots)...

    Started by mxs‎, 01-18-2015 02:32 PM
    • Replies: 3
    • Views: 258
    01-19-2015, 06:32 AM Go to last post
  47. [Study design] is this a version of crossover design

    Hello, I came across a set of data comparing 2 medical approaches in terms of several continuous variables (Primary objective is compare A to B). ...

    Started by drmb‎, 01-16-2015 08:37 AM
    • Replies: 0
    • Views: 179
    01-16-2015, 08:37 AM Go to last post
  48. [Clustered Robust Standard Error] - Custering

    I am investigating the effects of age and exercise in protein expression in mouse motor neurons. I have four groups each with a limited number of...

    Started by brajo083‎, 01-15-2015 06:06 PM
    cluster analysis, logistic regression, regression, robust
    • Replies: 1
    • Views: 190
    01-15-2015, 08:41 PM Go to last post
  49. Thankfor for help in evaluating survival prognosis

    Hi! I'am investigating into the survival between two cohorts of incident patients. One historical (1986-1996) and one contemporary (2002-2012). I...

    Started by polarkakan2‎, 01-14-2015 04:51 PM
    • Replies: 1
    • Views: 335
    01-14-2015, 06:56 PM Go to last post
  50. Post Need help for selecting method

    I have a 4-group of data.in each group,there are 2 subcolumns which are before and after treatment.to analyse this which statistical method should I...

    Started by Yusupjan‎, 01-13-2015 05:01 PM
    • Replies: 1
    • Views: 393
    01-14-2015, 03:14 PM Go to last post
  51. Disproportional Sampling for Uneven Case Controls

    Hello, I am looking to do a random sampling analysis of a case/control dataset containing 6X as many controls as cases. Therefore, I need to...

    Started by rdoan‎, 01-13-2015 09:33 AM
    case control, disproportional sampling, random sampling, sampling
    • Replies: 0
    • Views: 170
    01-13-2015, 09:33 AM Go to last post
  52. Help on bachelor's thesis!

    Hey everyone! I'm trying to analyse my bachelor's thesis data in SPSS, but I'm not entirely confident I'm using the right methods. Could you...

    Started by Scoltey‎, 01-12-2015 05:04 AM
    • Replies: 0
    • Views: 418
    01-12-2015, 05:04 AM Go to last post
  53. Type 1 or type 3 analysis?

    I'm trying to fit various models (I had been doing negative binomial, but then had to switch to Poisson in some cases because of the model being...

    Started by wernie07‎, 01-11-2015 01:11 PM
    • Replies: 0
    • Views: 308
    01-11-2015, 01:11 PM Go to last post
  54. Use of tnm as continuous variable in univariate or multivariate analysis

    Hello, I hope I put this post in the correct group. May I use TNM stage (1,2,3....), N stage (0,1,2,3.....) or grade (1,2,3,4....) as...

    Started by greeklatin‎, 01-08-2015 02:00 PM
    • Replies: 2
    • Views: 226
    01-09-2015, 03:56 AM Go to last post
  55. Multiple imputation

    I am doing a research about Aids in my city in Yemen. Unfortunately I have many missing data . So I used SPSS multiple imputation. I am not sure...

    Started by Alyamani‎, 01-07-2015 07:29 AM
    • Replies: 2
    • Views: 220
    01-08-2015, 01:22 AM Go to last post
  56. Using survival analysis to predict scope of truncated data

    I'm not sure I'm thinking about this correctly, and would be grateful for any insight as I think the problem is analogous to one that comes up in...

    Started by rboucherdata‎, 01-07-2015 05:30 PM
    event history analysis, forecasting, survival analysis, truncation
    • Replies: 0
    • Views: 172
    01-07-2015, 05:30 PM Go to last post
  57. Help with kaplan meier analysis in SPSS

    HI! Thank you very much in advance for helping with my post! I am a phd student, I do surgical research at the carotid artery. My current...

    Started by phdSPPShelp‎, 01-04-2015 09:59 AM
    biostatistics, spss, survival analysis
    • Replies: 2
    • Views: 343
    01-07-2015, 05:13 PM Go to last post
  58. Question about population matching procedure

    Good evening everyone, I am currently conducting a clinical trial where I am taking an intervention population (which is referred to a new...

    Started by cardgage‎, 01-06-2015 10:42 PM
    matching, matching data
    • Replies: 1
    • Views: 204
    01-07-2015, 02:56 AM Go to last post
  59. limts and probability

    I am looking at code and I do not understand it. The values T and R are natural logs and the expression given is (T-R)^2 -(std error)^2. I do ...

    Started by Angus McLean‎, 01-06-2015 06:28 PM
    • Replies: 1
    • Views: 163
    01-06-2015, 09:48 PM Go to last post
  60. Prediction versus Association: what's the difference?

    Hi! I wonder how to evaluate the performance of the tools that associate a variable (example: SNP, gene...) with a phenotype. In a few papers ,...

    Started by scratchscratch‎, 12-29-2014 06:17 AM
    • Replies: 0
    • Views: 302
    12-29-2014, 06:17 AM Go to last post

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