Search results

  1. U

    Help determining start values of coefficients for a nonlinear model

    Hi everyone. For a dataset consisting of three quantitative variables, H, M and W I have to build a non linear model of this form: E(H)=b0+b1*M+(W/(b3+b4*M)). I tried using the "nls()" function in R, but I don't know how to determine the start values of the coefficients, b0, b1, b3 and b4. Can...
  2. U

    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. U

    Doubt on a model

    Hi everyone, for an universitary assignment, I have to model one dependent variable H based on two other independent variables, M and W; the model I have to fit to the data is this: E(H)=b0+b1*M+(W/(b3+b4*M)) do you have any clue on what kind of model this is and how can it be adapted in R?
  4. U

    Should I consider this variable continuous or discrete?

    Hi everyone. I'm working on a dataset in which there are n = 24 observation on subjects, tested for physical resistance. The goal is to evaluate the burnt calories (first variable) based on the body mass in kilos (second variable) and the work level (third variable). The column of the variable...
  5. U

    When are non-parametric tests more desireable than a scale transformation when working on non-normal data?

    When, during an exploratory analysis, should one go for a robust test instead of a logaritmic/Box-Cox transformation of a variable if the Shapiro-Wilk test to verify the normality of the distribution of said variable is significant? Also, if I transform a variable with a logaritmic or a box-cox...
  6. U

    Help: working on a dataset on logaritmic scale

    Hi, for a university project I currently have to analyze a dataset inherent to a cluster of stars, in which the two main variables are luminosity and temperature of each star. The main goal is to validate the normality hypothesis in both variables (usually I go with >qqnorm() + >qqline() +...
  7. U

    Is multidimensional ROC Curve Analysis a thing?

    Hi, I'm a student of statistics and right now, in my course, we're studying validation of diagnostic tests. While learning about ROC Curves and AUC, I was wondering if does considering ROC Curves in the multivariate context make sense, and if so, how's the analysis performed and which are the...