# biostatistics

1. ### calculate the 95% confidence interval for the mean lead concentration for all the children in the school

Please answer the following problem and provide a step by step explanation please The concentration of lead in the bloodstream was measured for a sample of 50 children from a large school near a busy main road. the sample mean was 10.12 ng ml and the standard deviation was 0.64 ng ml¯...
2. ### Help! What analysis should be performed on a dataset like this?

I'm sorry but I really need help on how to perform an analysis on these data. This dataset, in which is studied the number of calories emitted during exercise on 24 observations (subjects), consists of three variables, all quantitative: ho (heat output) is the dependent variable and is the...
3. ### Adjusted OR

How to find adjusted OR as given in Table 6 in spss? The procedure followed to get it like i found binary logistic regression is used to find crude OR using single indep. variable.
4. ### Missing data-can a heterogenous small subgroup affect the outcome of analysis?

Hello everyone, I'm confronting an obstacle when doing clinical research, the problem is described as follows: There are 141 pieces of patients' data, and I want to use 2 formulas to analyze them. Formula A only needs 2 variables (Va, Vb), Formula B need 5 variables (Va, Vb, Vc, Vd, Ve). As you...
5. ### Kruskal-Wallis, Dunn's Test, Multiple Mann-Whitney-U Test

Hello everyone, I am studying immue cell distribution in different types of nontomourous (n=66), precancerous (n=67) and malignant tissues (n=48) in a single patient cohort. As you can see in the violin plot attached below, I started out by applying the K-W test to compare the distribution in...
6. ### modeling an outcome that has a range from [-0.158 ; 1 ]

Hello everyone, I am trying to model a quality of life score that has a range [-0,158 ; 1], where values equal to one indicate the patient is fully healthy, values equal to 0 indicate the patient is dead, values smaller than 0 indicate a health state that is worse than death. I assume general...
7. ### Nonparametric Friedman test - repeated measures and repeated subjects

Hi all, I would appreciate some advice on the most appropriate nonparametric test to evaluate the impact on some measures when subsampling my original datasets. Number of subjects: 9 Number of original datasets: 14 (some subjects have multiple sessions; 3 subjects have 2 sessions; 1 subject has...
8. ### Which statistical tests should be performed?

Hi, I did experiment to compare the effect
9. ### What are the differences between predictive and prognostic models?

In the context of survival analysis, what is a prognostic model and a predictive model? How are they defined mathematically? And can one have a prognostic model for survival prediction? Thank you for taking the time to read my questions and provide your helpful answers.
10. ### Survival analysis at few dates: glms? logrank? cox ?

Hello, In many documentation I have read that Kaplan-Meier curves followed by logrank test and/or cox models are the most recommended statistical methods to analyse Survival and test for different factors that may impact the Survival. However, I have also heard that these are suitable if I...
11. ### Power analysis

Dear all, First of all I would like to thank you for helping me with this question. For my research I investigated 23 patients. I looked at there range of motion of the shoulder and investigated the angle at which a dislocation/relocation occurred during forward flexion (FF) and abduction...
12. ### Book Review - Essentials of Bio statistics: An overview with the help of software

Would like to receive the review for the following book Essentials of Bio-statistics: An overview with the help of software www.ijsmi.com/book.php This book intends to provide an overview of biostatistics concepts and methodology through the use of statistical software. It helps clinicians...
13. ### Best statistical method for CFU/ml?

I have sets of data in CFU/ml for different sampling sites collected in two different seasons. 1. How do I compare the CFU/ml between sampling sites within one season? 2. How do I compare the CFU/ml in different seasons of the same sampling site? one-way ANOVA?
14. ### Regression Analysis - Beta Values

I have a question on a sample test for my upcoming prelims and I am unsure how to answer a question, scenario and questions below... A study measured dental measurements from the center of the pituitary to the pterygomaxillary fissure (measured in mm) for 11 girls and 16 boys at ages 8, 10, 12...
15. ### Statistical Tools for Analysis of Effect of Light, Temp, CO2, and pH on Growth Rate

My question is, what may be the ideal tools to analyze the data from this experiment and what are some resources you can recommend to learn about them (textbooks, website, etc.). I'm also just starting to learn R so feel free to work that in there. I'm designing undergraduate research to be...
16. ### Problem with normalization and - proteomics analysis (LC-MS)

Hi folks, I am working with proteomics data, containing mainly LC-MS and NMRI analysis. Firstly, I must normalise data to give valuable compound for biostatistics analysis such as data imputation. I have never had to deal with such data. Can you advise me on which method to choose (I usually...
17. ### reference interval determination

Hi all, I was wondering if I could ask for some help from some more statistically inclined persons than myself. We are trying to determine a reference interval for a new machine that measures a particular protein in the blood of horses. This machine has never been used before in horses...
18. ### interpretation of a negative risk difference

Hi, I am reviewing a cohort study and trying to make sense of the results. When considering mortality they presented their results as a risk difference which is a little different to what I normally see. Usually reported is RR or OR. In this case the results give a negative number. -35% (95%CI...
19. ### Rewriting integration by summation

Suppose that n individuals have lifetimes represented by random variables T_1, T_2, \ldots, T_n. Instead of the observed values for each lifetime, we have a time t_i' which we know is either the lifetime or censoring time. Let us define a variable \delta_i=I(T_i=t_i') that equals 1 if...
20. ### efficient R code

I have the following code in R to creat .ped file and .map file that is used in Plink "open-source whole genome association analysis toolset" I need more efficient R code since the data I have is 905460 rows and 1120 columns and it takes forever to run , " I didn't get results for 2 days...