What is the value of x?
2 answers:
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Answer:
a) P(75 < x < 80 ) = 0.2088
b) The probability that average height of all humans less than 65
P( X < 65 ) = 0.0495
Step-by-step explanation:
<u><em>Step(i)</em></u>:-
Given mean of the Population = 72
Given variance of the Population = 18 inches.
Standard deviation of the Population = √18 = 4.242
Let 'x' be the random variable in Normal distribution
a)
Given X₁ = 75
Given X₂= 80
The probability that average height of all humans between 75 and 80
= | A ( 1.885) - A( 0.70721|
= 0.4699 - 0.2611
= 0.2088
P(75 < x < 80 ) = 0.2088
b)
<u><em>Step(ii)</em></u>:-
Given X₁ = 65
The probability that average height of all humans less than 65
P( X < 65 ) = P( Z < - 1.650 )
= 1 - P( Z > 1.650)
= 1 - ( 0.5 + A (1.650))
= 0.5 - A( 1.65)
= 0.5 - 0.4505
= 0.0495
The probability that average height of all humans less than 65
P( X < 65 ) = 0.0495
has a horizontal tangent line at
, and it's clear from the plot that
is increasing to the left and descreasing to the right. This means
when
, so there is an inflection point there and only statement II is true.
Statement III is not true because critical points only occur where or (possibly) when
is undefined. Clearly
when
.