Questions: Assume that adults have IQ scores that are normally distributed with a mean of μ=105 and a standard deviation σ=15. Find the probability that a randomly selected adult has an IQ less than 126.
The probability that a randomly selected adult has an IQ less than 126 is
(Type an integer or decimal rounded to four decimal places as needed.)
Transcript text: Assume that adults have IQ scores that are normally distributed with a mean of $\mu=105$ and a standard deviation $\sigma=15$. Find the probability that a randomly selected adult has an IQ less than 126.
Click to view page 1 of the table. Click to view page 2 of the table.
The probability that a randomly selected adult has an IQ less than 126 is $\square$
(Type an integer or decimal rounded to four decimal places as needed.)
Solution
Solution Steps
Step 1: Define the Normal Distribution Parameters
We are given that the IQ scores of adults are normally distributed with a mean μ=105 and a standard deviation σ=15.
Step 2: Calculate the Z-Score
To find the probability that a randomly selected adult has an IQ less than 126, we first calculate the Z-score for X=126 using the formula:
Z=σX−μ
Substituting the values:
Zend=15126−105=1521=1.4
Step 3: Determine the Probability
The probability that a randomly selected adult has an IQ less than 126 can be expressed as:
P(X<126)=Φ(Zend)−Φ(Zstart)
Where Zstart approaches negative infinity. Thus, we have:
P(X<126)=Φ(1.4)−Φ(−∞)=Φ(1.4)
Using the standard normal distribution table or a calculator, we find:
Φ(1.4)≈0.9192
Final Answer
The probability that a randomly selected adult has an IQ less than 126 is: