Question

The average daily high in Port Forlorn in July is found to have a mean of 25 degree celsius with a standard deviation of 5 degree celsius. On how many days is the temperature expected to top 30 degree celsius assuming a normal distribution

Answer 1

solution

Given that,

mean = = 25

standard deviation = =5

Using standard normal table,

P(Z > z) = 30%

= 1 - P(Z < z) = 0.30

= P(Z < z ) = 1 - 0.30

= P(Z < z ) = 0.70

= P(Z <0.52 ) = 0.70

z = 0.52 (using standard normal (Z) table )

Using z-score formula  

x = z * +

x= 0.52 *5+25

x= 57.6

x=58