Question

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. What percentage of pools having an acceptable pH level

Answer 1

Answer:

78.383%

Step-by-step 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%