Question

Suppose a local pizzeria delivers pizzas every day of the week and their delivery times are normally distributed with a mean of 30 minutes with a standard deviation of 4 minutes. Determine the interval that contains the middle 80% of delivery times.

Answer 1

interval in minutes = (24.88, 35.12)

Explanation:

we can use the following formula:

interval = population mean ± (z · σ)

• population mean = 30 minutes
• z for 80% = 1.28
• σ = 4 minutes

interval = 30 minutes ± (1.28 · 4 minutes)

interval in minutes = (30 - 5.12), (30 + 5.12) = (24.88, 35.12)