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  1. O

    Help with this easy exercise

    Great, let me know what you got
  2. O

    Help with this easy exercise

    Hi Eco , as you state it is really easy ... did you manage? You just need to keep the full equation, set z into X and Y, and do basic algebra, then use the 2 formulas E(aX+b) and E(x^2). {Z instead of X in your case} You can't separate the equation (like you separated E(x-μx) ) as there is a...
  3. O

    Help with this easy exercise

    Typo I'm sure I wrote : E (aX+b) =aE(X)+b
  4. O

    Help with this easy exercise

    You need to set Z into X and Y, Also use the following formula: σ^2=e(x^2)-(e(x))^2
  5. O

    Help with this easy exercise

    E (aX+b) =aE(X)
  6. O

    Chow test in logistics regression

    Hi Traore, What is poverty_1, poverty_2? dummy variable of categorical variable with 3 values? What are the possible values of poverty? The only male regression and the only female regression have less power than both sexes regression. Generally, a sample size of more than 1000 should be big...
  7. O

    Chow test in logistics regression

    Hi Traore, If the theoretical model says it should be significant, and the full model with boys and girls is significant, so poverty is significant. I expect that with a larger sample size the partial models will also be significant... PS what are the p-values of poverty in each of the 3 models?
  8. O

    Sample size considerations

    Hi CC How do you plan to predict? What do you want to predict? Is the prediction change over time? What test do you want to run?
  9. O

    Chow test in logistics regression

    Hi, You didn't answer all my questions :), so I will try to have a general answer. 1. Statistical tests with a greater sample size (60) will have greater power to identify smaller effect sizes than tests with a smaller sample size (30). If you want to get better intuition you may do a simple...
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    How to find the right test

    Hi BP, So the DV is the donation sum, and IV is the stress level? Do you mean 80 options of organizations and the participant decide to donate to one organization? How many participants? Do you have any other IVs?
  11. O

    Chow test in logistics regression

    Hi Traore, What is the dependent variable (DV)? and what are the independent variables (IV)? If for example, you have 30 boys and 30 girls Do you mean that when you run logistic regression over 30 boys or over 30 girls the IV poverty is not significant? And when you run it over 60 children...
  12. O

    Probabilty or reduction in likelihood?

    Hi Ron, You may just calculate the occupation percentage. for each day/week If you still want to calculate the probability that a random hour will be free it is a similar calculation. For example, you calculate t1, the number of 15 minutes period in the relevant period. For example, if it is...
  13. O

    Probabilty or reduction in likelihood?

    Hi Ron, Do you mean if you want to schedule a 45 min appointment on random hour what is the probability that it is not blocked by other appointment"? What is the goal of this calculation?
  14. O

    chi square test

    Hi Meena, What null assumption do you think you should use? How did you try to solve the question?
  15. O

    Does dummy coding produce a "high dimensional" dataset?

    Hi Amd, From a logical perspective, I would think about a categorical variable as only one dimension. Multiple linear regression formula with matrices: (least-squares model) B=((X'X)^(-1))*X'Y From the calculation perspective, when you calculate linear regression each additional dummy...
  16. O

    ARDL package

    Didn't use it yet Noetsi :)
  17. O

    Sample size, effect size and power.

    Another example: Trying to determine which person is higher? If you watch from a far distance (low power) you will not be able to distinguish between 178cm and 180cm (low effect) But you will be able to distinguish between 110cm and 180 cm (high effect) If you watch from a close distance...
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    ARDL package

    I can only assume you did something in a different way... may be you defined something else in "data"? You may always try to clean the workspace: Sessions => Clear Workspace Or write : "rm(list = ls())" ls() is the list of variables for example: > ls() [1] "model1" "x" so rm remove the list...
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    ARDL package

    Hi Noetsi, I didn't get any error > library(ARDL) To cite ARDL in publications use: Kleanthis Natsiopoulos and Nickolaos Tzeremes (2020). ARDL: ARDL, ECM and Bounds-Test for Cointegration. R package version 0.1.0. University of Thessaly, Department of Economics...
  20. O

    Sample size calc for two sample proportions

    Each group: n1=n2=(Zα/2+Zβ)^2 * (p1(1-p1)+p2(1-p2)) / (p1-p2)^2