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Forum: Biostatistics

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

  1. Total complications in both groups

    Hi, I have the following question: In my study I compare two kinds of surgery options. Group A has 9 patients and group B has 6 patients. When...

    Started by chabby‎, Yesterday 08:28 AM
    events
    • Replies: 9
    • Views: 129
    Today, 01:04 PM Go to last post
  2. Multiple imputation and ROC curve anlaysis

    Hi, I have searched extensively for a solution to the following problem, without success. I have used multiple imputation on SPSS 22 to create 5...

    Started by CE479‎, Yesterday 04:25 PM
    • Replies: 3
    • Views: 107
    Today, 10:09 AM Go to last post
  3. Sample size calculation for non-inferiority and superiority

    Dear all, I am little bit confused with dual statements which I read in the literatures and books. Some says that Non-inferiority studies requires...

    Started by kumarnaidu‎, 03-26-2015 06:30 AM
    • Replies: 4
    • Views: 230
    03-27-2015, 09:48 PM Go to last post
  4. Comparing rates of hospital episodes in different groups

    Hi there, I'm trying to compare the rates of hospital admissions in different groups. For example: 200,000 people live in the local area, and...

    Started by lewerdan‎, 03-24-2015 07:18 AM
    • Replies: 6
    • Views: 235
    03-27-2015, 11:32 AM Go to last post
  5. Discretization of a continuous variable

    He guys, I'm analyzing a research regarding patients and their risk factors for developing a certain side effect. If i enter age as a continous...

    Started by XPeriment‎, 03-26-2015 06:06 AM
    • Replies: 1
    • Views: 100
    03-26-2015, 06:20 AM Go to last post
  6. Three way anova for repeated measure

    Hi all, I am struggling with how to properly fit a three way anova using STATA. It keeps giving me this error message "could not determine...

    Started by Ralph84‎, 03-24-2015 01:47 PM
    • Replies: 5
    • Views: 226
    03-25-2015, 07:33 AM Go to last post
  7. Futility analysis sample size

    Hello, I have been asked to determine the sample size needed to demonstrate futility in a small study. I suggested going the "traditional route" and...

    Started by jcr‎, 03-24-2015 09:55 AM
    futility, interim, sample size, stopping, type 2 errors
    • Replies: 2
    • Views: 89
    03-24-2015, 10:10 AM Go to last post
  8. One or Two Way ANOVA?

    Hi all, Just had a quick question regarding whether or not I should be using a one or two way ANOVA to see the effect of caffeine on heart rate....

    Started by squath‎, 03-20-2015 10:55 PM
    anova, biostats, trials
    • Replies: 4
    • Views: 244
    03-23-2015, 11:10 AM Go to last post
  9. Comparing proportions

    I am planning ahead before starting an experiment and want to be sure that I can analyze the results statistically. I have two related questions,...

    Started by mpal‎, 03-21-2015 12:27 PM
    • Replies: 1
    • Views: 155
    03-23-2015, 09:22 AM Go to last post
  10. Determining whether the exponent of an allometric equation = 3

    I have derived several allometric (exponential) equations in the form Y=bX^a These relate body mass of wildebeest (Y) to linear body measurements...

    Started by Gnu‎, 03-17-2015 03:30 AM
    • Replies: 6
    • Views: 290
    03-23-2015, 08:56 AM Go to last post
  11. Question types of chi-square statistics

    :) hi all I want to know types of Chi-square statistics and their applications. Such as Pearson x2 and mantel-haenzel x2 and x2trend and ... .

    Started by hol‎, 03-19-2015 01:38 PM
    • Replies: 2
    • Views: 135
    03-20-2015, 01:35 AM Go to last post
  12. Comparing Measured and Predicted body Mass - Can I use the T-Test

    I have measured the body mass (Mb) of several wildebeest in kg. I have also measured other parameters including Girth (G), Length (L) and shoulder...

    Started by Gnu‎, 03-17-2015 03:15 AM
    • Replies: 3
    • Views: 200
    03-17-2015, 06:45 AM Go to last post
  13. Fat percentage affecting diet

    Need some help with some biostats. Studying for a final right now. I think i need to do a one-way anova and a post hoc comparison. I also need a full...

    Started by silentdogood‎, 03-16-2015 08:55 PM
    • Replies: 0
    • Views: 134
    03-16-2015, 08:55 PM Go to last post
  14. Comparing two %, what test can I use?

    Good afternoon forum fellows, I am currently conducting a prospective research study at my hospital. I haven't used my stats skills in awhile and...

    Started by jyw003‎, 03-15-2015 02:52 PM
    • Replies: 3
    • Views: 187
    03-16-2015, 07:49 PM Go to last post
  15. Range, does it matters ?

    Hello I am slightly confused about something. I will try to illustrate. Let's say that if one takes a medication to treat a condition, the...

    Started by Yankel‎, 03-15-2015 03:21 PM
    • Replies: 3
    • Views: 212
    03-16-2015, 03:18 AM Go to last post
  16. Mantel's Chi 2 test - how to perform

    Hello dear users, I have a question about Mantel's Chi 2 test and you are my last hope :). I want to perform Mantel's Chi 2 in SPSS but cant find...

    Started by badibad‎, 03-13-2015 02:14 PM
    • Replies: 3
    • Views: 213
    03-14-2015, 02:20 PM Go to last post
  17. Interpreting hierarchical logistic regression results

    I conducted a hierarchical logistic regression examining the association among several different types of childhood adversities, mental disorders,...

    Started by elaine1827@yahoo.com‎, 03-13-2015 09:48 PM
    • Replies: 1
    • Views: 152
    03-13-2015, 10:31 PM Go to last post
  18. Question Comparing means with zero-inflated data in SPSS

    Hi everybody, I whish to know how to compare means with zero-inflated data. I tried to perform an ANOVA test but obviosuly it's impossible since...

    Started by Reset85‎, 03-12-2015 12:09 PM
    anova, generalized linear models, spss, zero inflated
    • Replies: 0
    • Views: 164
    03-12-2015, 12:09 PM Go to last post
  19. T test on whole sample or on averages

    Background: Consider the following experiment: There are two groups of subjects, Group A have been treated with a drug that affects the muscle...

    Started by theblackalchemist‎, 03-10-2015 04:55 AM
    • Replies: 3
    • Views: 240
    03-12-2015, 06:25 AM Go to last post
  20. Repeated measures in a GLM, do I need to use a GLMM?

    Hi guys, So I have finished an experiment where I had 11 cages of mice building nests with 3 different materials. Each cage was given a material...

    Started by Daveinci‎, 03-10-2015 09:30 AM
    • Replies: 1
    • Views: 194
    03-10-2015, 02:30 PM Go to last post
  21. what stats to use?

    Dear All, As I am not experienced in stats I would like to ask for some stats suggestions for a study. study one: control impact with one...

    Started by jg.marine‎, 03-10-2015 11:56 AM
    biostatistics, ecological statistics, permanova, r software, unbalanced
    • Replies: 0
    • Views: 115
    03-10-2015, 11:56 AM Go to last post
  22. Measurement error in binary outcome variable for a case-control study

    I am currently working on a case-control study on a rare disease using a large patient database. Using conditional logistic regression I will...

    Started by marsh_randy‎, 03-05-2015 11:57 AM
    • Replies: 3
    • Views: 257
    03-06-2015, 07:44 AM Go to last post
  23. Survival Analysis - Rate covariates

    hi all! I'm not too experienced with survival analysis, so I'm hoping to get some feed back regarding our design / study: Start Date: Date...

    Started by jamesmartinn‎, 03-05-2015 10:51 AM
    • Replies: 0
    • Views: 136
    03-05-2015, 10:51 AM Go to last post
  24. 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, 03-04-2015 12:27 PM
    • Replies: 1
    • Views: 143
    03-05-2015, 09:02 AM Go to last post
  25. 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, 03-04-2015 09:07 AM
    • Replies: 2
    • Views: 112
    03-05-2015, 08:48 AM Go to last post
  26. 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 05:09 AM
    • Replies: 4
    • Views: 284
    03-05-2015, 08:02 AM Go to last post
  27. 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 04:17 PM
    confidence intervals, paired data, ratio of means
    • Replies: 7
    • Views: 420
    03-05-2015, 12:32 AM Go to last post
  28. 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, 03-04-2015 04:52 AM
    • Replies: 6
    • Views: 218
    03-04-2015, 01:53 PM Go to last post
  29. 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 09:25 AM
    • Replies: 2
    • Views: 281
    03-04-2015, 11:28 AM Go to last post
  30. 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 10:12 AM
    case control; matched, stata commands
    • Replies: 5
    • Views: 419
    03-02-2015, 10:08 AM Go to last post
  31. 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 03:52 PM
    • Replies: 0
    • Views: 157
    02-27-2015, 03:52 PM Go to last post
  32. 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 09:35 AM
    • Replies: 2
    • Views: 223
    02-27-2015, 12:06 PM Go to last post
  33. 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 02:56 AM
    life expectancy, survival analysis
    • Replies: 0
    • Views: 129
    02-26-2015, 02:56 AM Go to last post
  34. 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 10:43 PM
    • Replies: 0
    • Views: 137
    02-25-2015, 10:43 PM Go to last post
  35. 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 09:57 AM
    • Replies: 3
    • Views: 212
    02-25-2015, 04:46 PM Go to last post
  36. 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 04:32 PM
    logistic regression
    • Replies: 3
    • Views: 239
    02-24-2015, 02:47 PM Go to last post
  37. 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 08:56 AM
    • Replies: 3
    • Views: 325
    02-23-2015, 10:43 AM Go to last post
  38. [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 05:52 PM
    • Replies: 3
    • Views: 321
    02-23-2015, 09:19 AM Go to last post
  39. 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 04:54 AM
    gompertz, logistic
    • Replies: 3
    • Views: 215
    02-19-2015, 12:52 PM Go to last post
  40. 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 06:54 PM
    • Replies: 6
    • Views: 445
    02-13-2015, 04:59 PM Go to last post
  41. 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 10:29 AM
    • Replies: 0
    • Views: 186
    02-12-2015, 10:29 AM Go to last post
  42. 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 09:08 PM
    • Replies: 0
    • Views: 139
    02-11-2015, 09:08 PM Go to last post
  43. 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 10:18 AM
    • Replies: 2
    • Views: 200
    02-11-2015, 02:49 PM Go to last post
  44. 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 02:48 PM
    • Replies: 6
    • Views: 327
    02-10-2015, 02:48 PM Go to last post
  45. 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 10:14 AM
    • Replies: 4
    • Views: 184
    02-10-2015, 11:19 AM Go to last post
  46. 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, 02-09-2015 11:55 PM
    • Replies: 0
    • Views: 161
    02-09-2015, 11:55 PM Go to last post
  47. 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 01:19 PM
    anova, conditions, one-way
    • Replies: 2
    • Views: 311
    02-06-2015, 01:07 PM Go to last post
  48. 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 12:48 PM
    chi2, graph menu
    • Replies: 0
    • Views: 173
    02-06-2015, 12:48 PM Go to last post
  49. 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 03:15 AM
    • Replies: 10
    • Views: 424
    02-05-2015, 12:13 AM Go to last post
  50. 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 10:39 PM
    • Replies: 12
    • Views: 523
    02-04-2015, 05:58 PM Go to last post
  51. 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 07:37 AM
    • Replies: 2
    • Views: 209
    02-03-2015, 11:04 AM Go to last post
  52. 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 06:18 AM
    • Replies: 4
    • Views: 265
    02-03-2015, 02:55 AM Go to last post
  53. 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 01:27 AM
    adonis, different groups, permanova, r program
    • Replies: 0
    • Views: 167
    02-03-2015, 01:27 AM Go to last post
  54. 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 01:54 PM
    central limit theorem, confidence intervals
    • Replies: 2
    • Views: 274
    02-02-2015, 08:40 AM Go to last post
  55. 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 09:59 PM
    • Replies: 0
    • Views: 181
    02-01-2015, 09:59 PM Go to last post
  56. 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 09:06 AM
    • Replies: 2
    • Views: 297
    01-30-2015, 03:04 AM Go to last post
  57. 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 10:11 PM
    • Replies: 1
    • Views: 206
    01-30-2015, 02:53 AM Go to last post
  58. 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 02:14 PM
    • Replies: 2
    • Views: 218
    01-30-2015, 02:46 AM Go to last post
  59. 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 04:58 PM
    • Replies: 0
    • Views: 165
    01-29-2015, 04:58 PM Go to last post
  60. 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 03:18 AM
    • Replies: 1
    • Views: 319
    01-28-2015, 04:43 PM Go to last post

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