Forum: Biostatistics

Hello statistics peoples, I'm not sure if this is the right forum so please do point me in the right direction if not. I'm looking at using...

Dear Friends I am working on a project on pediatric cancer. The details are given below. 1. 34 patients underwent PET scan and CT scan at 2...

Hello all, I have the hazard ratios (about 50) from an existing Cox model of survival based on national data, which calculates expected survival...

Hi, I was wondering whether anyone could point me in the direction for help on performing a DA on a two-factor (2 IVs each with 2 groups) design....

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...

I'm trying to analyze a crossover clinical trial with 2 treatment periods: study drug and placebo. I use SAS. I wasn't sure if I should use proc...

In a logistic regression, I have a categorical variable (3 levels) which the type III analysis of effects shows as non-significant (p >.05). Yet in...

Is there a statistical test to show that a sample is representative of a population? or is just fufilling some criteria, ie sample source, data...

I need to compare two recombination frequencies, and have previously used heterogeneity Chi Sq tests, but have recently been told that I cannot do...

Hi, I am new with Factor Analysis, and need help to determint the cut off. For instance; I will measure the knowledge with 10 variable. How would I...

I would like to compare eleven different means ± std. error using a one-way ANOVA with Tukey's multiple comparisons. This seems like a...

How is it possible to determine the number of estrous cycles in dogs when the occurrence of the cycle is given. For instance, when the...

I recent stumbled upon a formula for Prevalence ratio which is (observed prevalence)/(Expected prevalence) with Observed prevalence is (Total...

We have 4 groups of subjects. Each group is given a different drug. We measure expression of a protein at time zero and at 3 time-points. We want...

Hi everyone, I'm trying to figure out how to run an appropriate comparison for clutch sizes of birds. Ultimately, I want to compare clutch size of...

I am trying to figure out how to calculate an estimated hazard ratio associated with a specific variable. I have the estimate and standard errors...

Have two data sets. One a set of calibrated estimations, another actual values. I am trying to calculate mean absolute percent error for the sets. ...

Hi everyone. I'm experiencing some confusion as to what level the data should be normal. For instance, in an unpaired data set, where some...

Hi I would like to compare some epidemiological findings in my study with similar findings in other studies. The problem is: 1. I don't know...

Suppose a pharmaceutical company wants to conduct a post-marketing clinical trial. It needs to recruit patients through retail pharmacies. Suppose...

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...

Hi there, This is my first post to forum. Have big problem. I have data about concentration of three chemicals (three traits) in plants from 30...

My assay has a lower limit of detection of 10. How do I include data below this point in my analysis? Should I enter them as 10 or 0 or is it not...

Hi, there, This is my first post here, and I hope that I can get some help here. It is bit long, so please bear with me. I am currently doing...

Hi, 2 days ago I ask about logistics regression, and LINK gave me a good solution for it. It worked. But then after I compare the result between...

Hi All, I sampled crickets weekly over 5 weeks from the same population, and measured their body size. Half of the crickets were taken from...

I have developed a risk scoring system that I'm trying to validate. It was originally developed in one cohort, and I am now validating it in a new,...

THE SITUATION: I am preparing a 420,008 observation Cox Proportional Hazards Regression model with 4001 indicator variables. The 4001st indicator...

Hi, first post. I am interested in calculating the areas under two survival curves (treatment group and control group) in an RCT; actually I am...

Hello guys! I want to calculate the prevalence of transfusion transmitted viral infection (Here HIV, Hepatitis B and Hepatitis C will be tested) in...

Hi everyone :wave: I'm studying GEE at the moment and I don't understanding the passage below. Could if anyone kindly explain to me in...

Hay , first Q on this forum.. ok so I need to perform a permanova analysis of some data 21 variables (7 species in triplicate) and 7 observations...

I am going to perform an RCT comparing a treatment to a control. The study has 3 time points, namely, pre-treatment, post-treatment, and 1-month...

Can anyone help get my head a bit clearer on this one? I have completed a cross-sectional study looking at the prevalence of adherence to a...

Hi, I am comparing behavioural data collected at two populations. Generalised linear models were used with a behavioural trait as a response...

Hi, I have data on Hiv and need help with calculating the CI. The information I have are: 1. Estimated number people are infected t.ex. 320 2....

Hello, I collected data for an ecology project. There are two variables: body size and latitude. Hypothesis: As lat decreases, body size...

Hi there, I try to quantify the results from a test between a treatment and placebo group using Cohen's d evaluated as below; d=((μt-μp...

I am trying to design a vaccine study. The objective of the study is to determine if vaccine exposure contributes to an increased risk in developing...

I have a bimodal distribution in my data. I know that all parametric and non-parametric tests become unreliable with bimodal datasets, and that it...

Hi! My thesis dataset includes 2 variables (lay date and incubation period) that are integers, non-normal and have unequal variances. I'd like to...

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

Anyone can help me to firgure out the sample size calculation in cox regression? Are there any simple formula or calculators for it? Thanks

I have a four period crossover study where subjects take one of four treatments A to D in four different periods, during each period there response...

Hi all, any help here will be greatly appreciated.. I have a 2 x2 matrix i have compose from data collected Epibiont NIS on Basibiont NIS = 1...

Hi, I would like to compare two groups, one treated, one control. Usually, I would simply use a t-test, assuming normal distribution and equal...

Hi I tested if individuals were positive for 3 different pathogens at 4 different point of times. For the analysis I used chi-square test. The...

I am sampling for a microbe using a presence/absence detection method near the Poisson limit. Assuming that my method can detect 1 CFU no matter...

Hi Everyone, I have a dataset made up of incubation periods for first-laid and second-laid eggs (nest is the sampling unit) that I want to compare...

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,...

Hi Forum I am having trouble trying to find a way of estimating missing data from a project I have been working on and I hope that someone can...

Hello! I'm working on relative survival and so, I'm using life tables. My problem concerns the terminology linked to these tables. Could you help...

Hello all, I would like to see what the pain of a patient is before and after an opperation. But my data is not fitting the assumptions of ANOVA....

I'm a social psychologist at a nonprofit organization for people with cerebral palsy and other disabilities. We're anticipating a two-year project...

Hello everyone! I want to model a generalized SIR epidemic in a closed population using a discrete time markov chain. The susceptibles become...

Hi everyone: I really appreciate all of the great posts on here! I'm trying to wrap my head around a couple of things. First of all, a bit of...