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. Based on this information, what is the probability of a student reading at more than 1400 words per minute after finishing the course?
A) 0.0202
B) 0.5207
C) 0.4798
D) 0.9798

Question

Quizplus · Accepted Answer

To find the probability of a student reading more than 1400 words per minute, we use the Z-score formula: $Z = \frac{X - \mu}{\sigma}$, where $X$ is the value of interest (1400 words per minute), $\mu$ is the mean (950 words per minute), and $\sigma$ is the standard deviation (220 words per minute). Plugging in the values, we get $Z = \frac{1400 - 950}{220} = \frac{450}{220} \approx 2.045$. Looking up 2.045 in the standard normal distribution table or using a calculator gives a right-tail probability of approximately 0.0202, indicating the probability of a student reading more than 1400 words per minute is about 2.02%.

Students Who Have Completed a Speed Reading Course Have Reading