Question

On a planet far far away from Earth, IQ of the ruling species is normally distributed with a mean of 110 and a standard deviation of 16. Suppose one individual is randomly chosen. Let X = IQ of an individual. find the q1 and q3

Answer 1

Explanation:

First, we need to find the z-scores for q1 and q3.

Q1:

Using the formula for z-score, we get:

z = (x - μ) / σ

where x is the IQ score we want to find the z-score for, μ is the mean IQ of the population, and σ is the standard deviation of the population.

For the first quartile (q1), we want to find the z-score such that 25% of the population has an IQ score below that value. From the standard normal distribution table, we find that the z-score corresponding to a cumulative area of 0.25 is -0.674.

So we have:

-0.674 = (x - 110) / 16

Solving for x, we get:

x = 99.8

Therefore, q1 is approximately 99.8.

Q3:

Similarly, for the third quartile (q3), we want to find the z-score such that 75% of the population has an IQ score below that value. From the standard normal distribution table, we find that the z-score corresponding to a cumulative area of 0.75 is 0.674.

So we have:

0.674 = (x - 110) / 16

Solving for x, we get:

x = 120.8

Therefore, q3 is approximately 120.8.