Answer:
78.383%
Explanation:
The pH of randomly selected swimming pools follows a normal distribution with mean 7.4 and standard deviation 0.22. A pool should have a pH between 7.2 and 7.8 so that chlorine treatment is effective.
Using z score formula
z = (x-μ)/σ, where
x is the raw score
μ is the population mean
σ is the population standard deviation.
For x = 7.2
z = 7.2 - 7.4/0.22
z = -0.90909
Probability value from Z-Table:
P(x = 7.2) = 0.18165
For x = 7.8
z = 7.8 - 7.4/0.22
z = 1.81818
Probability alue from Z-Table:
P(x = 7.8) = 0.96548
The probability of pools having an acceptable pH level(7.2 and 7.8)
= P(x = 7.8) - P(x = 7.2)
= 0.96548 - 0.18165
= 0.78383
Converting to percentage
0.78383 × 100
= 78.383%
The percentage of pools having an acceptable pH level is 78.383%