# (Solution) Math 225N Week 5 Assignment Evaluating Probability using the Normal distribution

Week 5 Assignment Evaluating Probability using the Normal distribution

Question

Ms. Wilson’s math test scores are normally distributed with a mean score of 73 (μ) and a standard deviation of 5 (σ). Using the Empirical Rule, about 99.7% of the scores lie between which two values?

Question

After collecting the data, Peter finds that the standardized test scores of the students in a school are normally distributed with mean 85 points and standard deviation 3 points. Use the Empirical Rule to find the probability that a randomly selected student’s score is greater than 76 points. Provide the final answer as a percent rounded to two decimal places.

Question

The number of pages per book on a bookshelf is normally distributed with mean 248 pages and standard deviation 21 pages. Using the empirical rule, what is the probability that a randomly selected book has less than 206 pages?

Question

The times to complete an obstacle course is normally distributed with mean 87 seconds and standard deviation 7 seconds. What is the probability that a randomly selected finishing time is greater than 80 seconds? Use the empirical rule

# Solution:

Question

Ms. Wilson’s math test scores are normally distributed with a mean score of 73 (μ) and a standard deviation of 5 (σ). Using the Empirical Rule, about 99.7% of the scores lie between which two values?

The Empirical Rule says that 99.7% of the data lies within three standard deviations of the mean. The standard deviation is 5. So, the data that lie within three standard deviations of 73 (between −3σ and 3σ) will be the data that lie in the range that is (5)(3)=15 units less than the mean (73) and more than the mean (73). So, the values 73−15=58 and 73+15=88 are within three standard deviations of the mean. About 99.7% of the x-values lie between 58 and 88

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