Question

Intelligence Quotient (IQ) scores are often reported to be normally distributed with μ=100.0 and σ=15.0. A random sample of 51 people is taken. Step 1 of 2 : What is the probability of a random person on the street having an IQ score of less than 98? Round your answer to 4 decimal places, if necessary.

Answer 1

Answer:

0.4470 = 44.70% probability of a random person on the street having an IQ score of less than 98.

Step-by-step explanation:

Normal Probability Distribution:

Problems of normal distributions can be solved using the z-score formula.

In a set with mean $\mu$ and standard deviation $\sigma$, the z-score of a measure X is given by:

$Z = \frac{X - \mu}{\sigma}$

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the p-value, we get the probability that the value of the measure is greater than X.

What is the probability of a random person on the street having an IQ score of less than 98?

This is the pvalue of Z when X = 98. So

$Z = \frac{X - \mu}{\sigma}$

$Z = \frac{98 - 100}{15}$

$Z = -0.1333$

$Z = -0.1333$ has a pvalue of 0.4470

0.4470 = 44.70% probability of a random person on the street having an IQ score of less than 98.