Students who have completed a speed reading course have reading speeds that are normally distributed with a mean of 950 words per minute and a standard deviation equal to 220 words per minute. If two students were selected at random, what is the probability that they would both read at less than 400 words per minute?
A) 0.4938
B) 0.0062
C) 0.00004
D) 0.2438

Question

Quizplus · Accepted Answer

To find the probability that a student reads at less than 400 words per minute, we first calculate the z-score: $z = \frac{400 - 950}{220} = -2.5$. Looking up -2.5 on the standard normal distribution table gives us approximately 0.0062. Since the question asks for the probability that both of two randomly selected students read at less than 400 words per minute, we square this probability: $0.0062^2 = 0.00003844$, which rounds to 0.00004, indicating a very low probability.

Students Who Have Completed a Speed Reading Course Have Reading