MHB Write ⊆ or ⊄ in the space provided.

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The discussion focuses on determining whether to use the subset symbol (⊆) or the not a subset symbol (⊄) in various mathematical expressions. The first two expressions are confirmed to be correct, while clarification is provided on the third expression involving the power set of the empty set. The fourth expression compares Cartesian products of natural and integer numbers, with a consensus that the left side contains distinct elements not found on the right. Overall, the participants engage in correcting and confirming the appropriate symbols for the given mathematical relationships.
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Write ⊆ or in the space provided.

(3,5) _____ [3,5]
[-1,4] ____ (-1,4)
{∅} _____ P(∅)
N * Z ____ Z * NMy Solution)




 
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KOO said:
Write ⊆ or in the space provided.

(3,5) _____ [3,5]
[-1,4] ____ (-1,4)
{∅} _____ P(∅)
N * Z ____ Z * NMy Solution)





Hi KOO! :)

The first 2 are correct.

Edit: see Evgeny.Makarov's post for the 3rd.

As for the 4th, can I assume you intended $\mathbb N \times \mathbb Z \underline{\qquad} \mathbb Z \times \mathbb N$?
If so then the left hand side has elements like (1,1) and (1,-1), while the right hand side has elements like (-1,1) and (1,1)...
 
I assume the first two questions are about intervals on the real line. Then I agree.

KOO said:
{∅} _____ P(∅)
Note that P(∅) = {∅}.
 
Evgeny.Makarov said:
Note that P(∅) = {∅}.

Good point.
Slipped on that one.
 
The standard _A " operator" maps a Null Hypothesis Ho into a decision set { Do not reject:=1 and reject :=0}. In this sense ( HA)_A , makes no sense. Since H0, HA aren't exhaustive, can we find an alternative operator, _A' , so that ( H_A)_A' makes sense? Isn't Pearson Neyman related to this? Hope I'm making sense. Edit: I was motivated by a superficial similarity of the idea with double transposition of matrices M, with ## (M^{T})^{T}=M##, and just wanted to see if it made sense to talk...

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