Question

I hope some one can help me!

The mean midday temperature recorded in June in a city in South California is 36_C, and the standard deviation is 3_C.
Assuming the data is normally distributed, the number of days in June when the midday temperature was between 39_C and 42_C is?

Answer 1

Given that:
μ = 36
σ = 3

Standardize x to z = (x - μ) / σ
P( 39 < x < 42) = P[( 39 - 36) / 3 < Z < ( 42 - 36) / 3]
P( 1 < Z < 2) = P( x < 2) - P( x < 1)
= 0.9772 - 0.8413
= 0.1359

(0.1359)(30)
= 4.0777
= 4 days