In: Statistics and Probability
A manufacturer knows that their items have a normally distributed lifespan, with a mean of 3 years, and standard deviation of 0.6 years.
If you randomly purchase 17 items, what is the probability that their mean life will be longer than 3 years?
Solution :
Given that,
mean = 
 = 3
standard deviation = 
 =0.6
n=17

= 
=3

= 
 / 
n =0.6 / 
17 = 0.1455
P(
 > 3) = 1 - P(
< 3)
= 1 - P[(
- 
) / 
< (3-3) /0.1455 ]
= 1 - P(z <0 )
Using z table
= 1 - 0.5
= 0.5
probability= 0.5