In: Statistics and Probability
5. A random sample of size n = 36 is obtain from a population with µ= 60 and standard deviation 12 (a). Describe the sampling distribution . (b). What is P(76.5 << 85.5 )?
Solution:
Given that ,
= 60
= 12
A sample of size n = 36 is taken from this population.
a)
Let
be the mean of sample.
Since the sample size n > 30 , therefore
the sampling distribution of the
is approximately normal with
Mean
=
= 60
SD
=
= 12/
36
= 2
b)
P(76.5 < x< 85.5 )
= P(X < 85.5 ) - P(X < 76.5 )
= P[(X -
)/
< (85.5 - 60)/12] - P[(X -
)/
< (76.5 - 60)/12]
= P[Z < 2.125] - P[Z < 1.375]
= 0.9832 - 0.9154..Use z table
= 0.0678