Question

Assume that adults have iq scores that are normally distributed with a mean of u = 105 and a standard deviation =20 find the probability that a randomly selected adult has an iq less than 129

Answer 1

P(X<129) ≈ 0.8849

Explanation:

I've attached a graph of the normal distribution to help you visualize the problem. To calculate this on a TI-84, we can use the normalcdf function to find the area between the end of the left-tail of the normal distribution to x=129, hence, we are finding P(X<129). We can write this as normalcdf(-1e99,129,105,20) ≈ 0.8849, therefore, the probability that a randomly selected adult has an IQ less than 129 is about 0.8849 or about 88.49% likely to occur.