Modeling the probability of a uniform point on [a,b]. Let f:R rightarrow R be defined as f(x):=(b-a)x+a. This function is an affine bijection between [0,1] and [a,b]. Let lambda be the Lebesgue measure on [0,1]. We can define a probability measure mu on R by setting mu(B):=lambda(f^{-1}(B>cap[a,b])) for any Borel measurable subset B of R^n . The corresponding c.d.f. is given by F(x)=0 if x<a, F(x)=1 if x>b and F(x)=f^{-1}(x)=(x-a)/(b-a) if x in [a,b].

benatudq

benatudq

Answered question

2022-10-30

Modeling the probability of a uniform point on [a,b]
I was given the following exercise : Explain how to define a probability measure on R that corresponds to the intuitive notion of an uniform point on [a,b].
And this is the solution:
Let f : R R be defined as f ( x ) := ( b a ) x + a. This function is an affine bijection between [0,1] and [a,b]. Let λ be the Lebesgue measure on [0,1]. We can define a probability measure µ on R by setting µ ( B ) := λ ( f 1 ( B > [ a , b ] ) ) for any Borel measurable subset B of R n . The corresponding c.d.f. is given by F ( x ) = 0 if x > b, F ( x ) = 1 if x > b and F ( x ) = f 1 ( x ) = x a b a if x [ a , b ].
I do not understand the question the exercise is asking. What is "the intuitive notion of an uniform point on [a,b]" ? Are they looking for a probability where all points in [a,b] have the same probability ?

Answer & Explanation

Martha Dickson

Martha Dickson

Beginner2022-10-31Added 20 answers

Step 1
Uniform means that the probability of a Borel set should be proportional to it's Lebesgue measure. Therefore we should define μ ( E ) = 1 b a m ( E ), where m is Lebesgue measure.
Step 2
Their solution is a strange way to arrive at the same μ.

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