Question

The amount of rainfall in January in a certain city is normally distributed with a mean of 3.1 inches and a standard deviation of 0.4 inches. Find the value of the quartile Q 1.

Answer 1

2.83

Explanation:

For a normally distributed data :

Mean = 3.1 inches

Standard deviation = 0.4 inches

Find the value of the quartile Q1:

The quartile Q1 represents the first quartile which is the Lower 25% of the distribution

25% = 0.25

Using the z-table :

0.25 = - 0.68

The z- score formula

Z-score = ( x - mean / standard deviation)

-0.68 = ((x - 3.1) / 0.4)

x - 3.1 = (-0.68 * 0.4)

x - 3.1 = - 0.272

x = - 0.272 + 3.1

x = 2.828

x = 2.83