. Suppose X ∼ Unif(−1, 3). Find the probabilities of the following events, both by hand calculation and with R’s punif function. (a) (X ≤ 2) (b) (X ≥ 1) (c) (−0.5 < X < 1.5) (d) (X = 0)

Respuesta :

Answer:

a) [tex] P(X \leq 2) = \frac{2+1}{3+1}= 0.75[/tex]

b) [tex] P(X \geq 1) = 1- P(X <1) =1-\frac{1+1}{3+1}= 1-0.5=0.5[/tex]

c) [tex]P(-0.5 <X <1.5)= P(X<1.5)- P(X<-0.5)= \frac{1.5+1}{4} -\frac{-0.5+1}{4}=0.625-0.125= 0.5[/tex]

d) [tex] f(x) = \frac{1}{3+1}= 0.25[/tex]

Step-by-step explanation:

Let X the random variable of interest and we know that the distribution is given by:

[tex]X \sim Unif (a= -1, b=3)[/tex]

And for this problem we can use the cumulative distribution function in order to solve the items:

[tex] F(x) =\frac{x-a}{b-a}, a\leq x \leq b[/tex]

Part a

We want to find this probability:

[tex] P(X \leq 2) = \frac{2+1}{3+1}= 0.75[/tex]

Part b

[tex] P(X \geq 1) = 1- P(X <1) =1-\frac{1+1}{3+1}= 1-0.5=0.5[/tex]

Part c

[tex]P(-0.5 <X <1.5)[/tex]

And we can calculate the probability with this difference:

[tex]P(-0.5 <X <1.5)= P(X<1.5)- P(X<-0.5)= \frac{1.5+1}{4} -\frac{-0.5+1}{4}=0.625-0.125= 0.5[/tex]

Part d

Since we have a continuous distribution the the probability for an unique value would be:

[tex] f(x) = \frac{1}{3+1}= 0.25[/tex]