Question

What is the approximate percentage of buyers who paid less than $1360?

Answer 1

less than $1360: 0.15%

less than $1440: 2.5%

Step-by-step explanation:

1360 is located at 3 standard deviations form the mean because

mean - 3(standard deviation) = 1600 - 3(80)

mean - 3(standard deviation) = 1600 - 240

mean - 3(standard deviation) = 1360

Then, using a standard normal distribution table, we can calculate the following probability

P(z < -3) = 0.15%

Therefore, the approximate percentage of buyers who paid less than $1360 is 0.15%

In the same way, $1440 is located at 2 standard deviations from the mean because

mean - 2(standard deviation) = 1600 - 2(80)

mean - 2(standard deviation) = 1600 - 160

mean - 2(standard deviation) = 1440

So, we need to find the following probability

P(z < -2) = 2.5%

Then, the approximate percentage of buyers who paid less than $1440 is 2.5%