modeling techniques

  1. A

    Statistical inference.

    Hi there, I would like to ask a couple of basic questions: 1. What is the difference between estimation and hypothesis testing? I mean are they two options for inference? or estimation of the parameters comes first and then we apply the hypothesis testing? 2. How can I determine what is...
  2. A

    Goodness of fit tests

    Hi there, Adding to my previous questions: 1. Why do I need goodness of fit test? I mean when I get a set of data should I always suggest a distribution for it and then do test the goodness of fit for this hypothesis? or it comes in sequence of :1.estimation 2.goodness of fit 3.hypothesis...
  3. N

    Compound poisson gamma model and biomass data

    I have some biomass data (total count -discrete- of individuals and total dry weight -continuous-) that I would like to model with environmental parameters recorded at different spatial scales (temperature -continuous-). My biomass data is zero inflated mainly due to scale inaccuracy and as a...
  4. IanB

    Stata Help Wanted

    Hello, Can someone offer some help with Stata. I need to know the following. 1) which are independent and which are dependent variables. 2) how to build a model using the variables I can post the spreadsheet and pay for help. I can supply my email address and Skype if suitable, or send me a...
  5. W

    Comparing self made models

    Hello! I have a quenstion about comparing models. Not models fitted by R itself, but user defined models. Ill explain through this example: Dataset: Tree Diameter Biomass Model1biomass Model2biomass 1 10 50 45 60 2 7 35 52...
  6. D

    When to use validation and derivation cohort?

    Hi everyone, I was wondering if there is any generic rules on when it's good to use a derivation and validation cohort on a dataset? So far I have only seen them being used for diagnostic tests. Also, if I use two datasets from two different studies to do this, do the datasets need to...
  7. 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...
  8. P

    Trouble with random factors glmm

    Hi. I am doing a behavioural ecology study on juvinile brown trout and want to perform a glmm (glmer, package lme4) to analyse the effect of activity, size and treatment on survival. The variables i am using and are: response-survival (dead or alive), fixed effects- size (continuous), activity...
  9. S

    Augmenting model predictions with another model

    Hello All, I am currently working on a problem which involves predicting the value of some variable (which I will call Y), based on a number of input variables (X_i, i = 1..N). The problem is that one of the input values (X_1, say) is actually a prediction of Y produced from an independent...
  10. M

    Model building using Training data and predoction of Target set with test data

    URGENT ! need help to build the Predictiive Model Hi, Need some help to solve the problem using right s/w(SPSS or execl) and approach . I have a raw attribute data for 430 restaurants. Training Data: The set contains information about 430 restaurants. The target variable for every row...