# The lengths of human pregnancies are normally

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Chapter 1 / Exercise 17
Introduction to Probability and Statistics
Beaver/Mendenhall
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13.The lengths of human pregnancies are normally distributed with a mean of 268 days and a standard deviation of 15 days. What is the probability that a pregnancy last at least 300 days? Round to four decimal places.
14.For women aged 18-24, systolic blood pressures are normally distributed with a mean of 114.8 mm Hg and a standard deviation of 13.1 mm Hg. If 23 women aged 18-24 are randomly selected,find the probability that their mean systolic blood pressure is between 119 and 122 mm Hg. Round to four decimal places.
15.What does it mean for the findings of a statistical analysis of data to be statistically significant? (The likelihood of getting these results by chance is very small)
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Chapter 1 / Exercise 17
Introduction to Probability and Statistics
Beaver/Mendenhall
Expert Verified
16.Why is it important to learn about bad graphs? (So that we can critically analyze a graph to determine whether it is misleading)17.In one region, the September energy consumption levels for single-family homes are found to be normally distributed with a mean of 1050 kWh and a standard deviation of 218 kWh. For a randomly selected home, find the probability that the September energy consumption level is between 1100 kWh and 1225 kWh. Round to four decimal places. (0.1982)18.A bank's loan officer rates applicants for credit. The ratings are normally distributed with a mean of 200 and a standard deviation of 50. If an applicant is randomly selected, find the probability of a rating that is between 200 and 275. Round to four decimal places. (0.4332)19.A student earned grades of 84, 78, 84, and 72 on her four regular tests. She earned a grade of 78on the final exam and 86 on her class projects. Her combined homework grade was 87. The four regular tests count for 40% of the course grade, the final exam counts for 30%, the project countsfor 10%, and homework counts for 20%. What is her weighted mean grade? Round to one decimal place. (81.2)20.Rolling a single die 53 times, keeping track of the "fives" rolled. (The procedure results in a binomial distribution.)21.Assume that a study of 500 randomly selected airplane routes showed that 482 arrived on time.