observational study

  1. A

    Choosing a statistical test.

    Hi, I am not very confident with stats but am needing help with analysing my data. I have observational data gained from observing marmosets over a period of five weeks. I am aiming to examine if there is any significant increase in time spent on certain behaviours over the course of these 5...
  2. R

    sample size for dichotomous outcome in retrospective observational study

    I really need some help here seeing if I can get this right. I seem to come up with something different every time. I am testing the hypothesis that there is no difference in the timing of removing chest tubes to the development of significant pleural effusions after surgery requiring drainage...
  3. O

    Longitudinal analysis of drug use data

    Hi all, I'm looking to conduct a longitudinal analysis using data from 5 waves of an observational research study. What I'm really interested in doing is seeing how changes in parental monitoring and some other family factors (i.e., cohesion, etc.) impact drug use and negative consequences of...
  4. V

    What test to compare bacterial growth in three areas with repeating variables?

    I have a dataset of number of bacterial colonies grown from 11 water samples taken from 3 different watersheds. I want to know if the land area, population, number of waste water treatment plant outfalls, and number of septic tanks in the watershed have any effect on the bacterial growth. The...
  5. S

    Tricky question: obtain r2 from a sample of 10 observations...that are unknown.

    OK, I've been trying to figure this problem out for 2 whole days... its tough, at least to me, and its driving me crazy! Any help would be GREATLY appreciated. From a sample of 10 observations, the following results were obtained: sum(Yi)=1110 sum(Xi)=1700 sum(XiYi)=205500...
  6. M

    Adverse drug reaction; multiple drugs, possible event(s) per patient. What analysis?

    Hello everyone, I am currently looking for the right method to compare the incidences of a given adverse drug reaction (infection) after the exposure to four different drugs (combinations are also possible) in an observational study. Some patients can function as a case and control (after...