Respuesta :
Answer:
Step-by-step explanation:
Applying the formula for normal distribution,
z = (x - u)/s
Where u = mean
s = standard deviation
x = the monthly utility bill in dollars
From the information given,
s = 23
u = 121
The probability that a randomly selected utility bill is between $110 and $130 is expressed as
P(110 lesser than or equal to x lesser than or equal to 130)
For 110
z1 = (110 - 121)/23 = - 11/23
z1 = - 0.4783
Looking at the normal distribution table,
The corresponding z score is 0.3192
For 130
z2 = (130 - 121)/23 = 9/23
z2 = 0.391
Looking at the normal distribution table,
The corresponding z score is 0.65173
P(110 lesser than or equal to x lesser than or equal to 130) = 0.65173 - 0.3192 = 0.33253
