This question is incomplete, the complete question is;
Let X denote the time in minutes (rounded to the nearest half minute) for a blood sample to be taken. The probability mass function for X is:
x 0 0.5 1 1.5 2 2.5
f(x) 0.1 0.2 0.3 0.2 0.1 0.1
determine;
a) P( X < 2.5 )
B) P( 0.75 < X ≤ 1.5 )
Answer:
a) P( X < 2.5 ) = 0.9
b) P( 0.75 < X ≤ 1.5 ) = 0.5
Explanation:
Given the data in the question;
The probability mass function for X is:
x 0 0.5 1 1.5 2 2.5
f(x) 0.1 0.2 0.3 0.2 0.1 0.1
a) P( X < 2.5 )
P( X < 2.5 ) = p[ x = 0 ] + p[ x = 0.5 ] + p[ x = 1 ] + p[ x = 1.5 ] + p[ x = 2 ]
so
P( X < 2.5 ) = 0.1 + 0.2 + 0.3 + 0.2 + 0.1
P( X < 2.5 ) = 0.9
b) P( 0.75 < X ≤ 1.5 )
P( 0.75 < X ≤ 1.5 ) = p[ x = 1 ] + p[ x = 1.5 ]
so
P( 0.75 < X ≤ 1.5 ) = 0.3 + 0.2
P( 0.75 < X ≤ 1.5 ) = 0.5