# Recent content by samr

1. ### Clarifying the concept of a probability mass function

Is the set equation required for PMF definition?
2. ### Clarifying the concept of a probability mass function

If so, I have a follow up question : in the article on Random Variables and Probability Distributions in Britannica, it says What about the 3d axiom of Kolmogorov? If if A and B are mutually exclusive then : P(A union B) = P(A) + P(B) I have seen the same omission in a Coursera course I am...
3. ### Clarifying the concept of a probability mass function

I am trying to understand what is the relationship between the concept of a probability mass function, and that of a probability measure. It seems to me that a probability mass function is simply a probability measure applied to a discrete random variable. Is that about right?
4. ### Trick question

The following question was posed to me : A person wants to compare between 2 versions of algorithms. He knows he has 100 False Negatives and wants the algorithms to find them. version 1 found 40 out of 100 False Negatives. version 2 found 90 out of 100 False Negatives. Is ver2 better?
5. ### Difference in differences estimation using a regression

I think I understood my mistake. While I have written that The first point is wrong - in standard diff-in-diff estimation, I have learned that one is supposed to calculate difference-in-difference between averages before, and averages after. I simply missed that. Thanks.
6. ### Difference in differences estimation using a regression

Hello, Difference in difference estimation implies calculating (P2-P1)-(S2-S1). That would give the result of the treatment. It seems to me that the estimation is valid for a specific time point, time 2 at this example. I have read however (for example, at wikipedia), that DiD estimation can...