In: Statistics and Probability
sample of 67,find probability of a sample mean being less than 20.1 if the mean = 20 and standard deviation=1.35
Solution :
Given that ,
mean = 
 = 20
standard deviation = 
 = 1.35
n = 67

= 
 = 20 and

= 
 / 
n = 1.35 / 
67 = 0.1649
P(
< 20.1) =   P((
- 
) / 
< (20.1 - 20) / 0.1649)
= P(z < 0.61) Using standard normal table.
Probability = 0.7291