Question

The mean price for regular gasoline at the pump was $2.877 per gallon and the standard deviation was $0.009 per gallon. A random sample of size 55 is drawn from this population. What is the probability that the mean price per gallon is less than $2.876?

Answer 1

Solution :

Given that ,

mean =   = 2.877

standard deviation = = 0.009

n = 55

= 2.877

=  / n = 0.009/ 55 =0.0012

P( < 2.876) = P[( - ) / < (2.876-2.877) /0.0012]

= P(z <-0.83 )

Using z table  

=0.2033   

probability= 0.2033