Concept explainers
The length of a Colorado brook trout is
a.
Find the probability that the length of a brook trout exceeds the mean.
Answer to Problem 76CE
Theprobability that the length of a brook trout exceeds the meanis 0.5.
Explanation of Solution
Calculation:
It is given that the lengths of a population of brook trout are normally distributed.
Normal distribution:
A continuous random variable X is said to follow normal distribution if the probability density function of X is,
Denote X as the length of a randomly selected brook trout. It is taken from a population of brook trout that are normally distributed.
Denote
The normal distribution is symmetrically distributed about its mean. From the concept of symmetry of a random variable X about
Thus, the probability that the length of a brook trout exceeds the mean is:
Hence, the probability that the length of a brook trout exceeds the mean is 0.5.
b.
Find the probability that the length of a brook trout exceeds the mean by at least 1 standard deviation.
Answer to Problem 76CE
Theprobability that the length of a brook trout exceeds the mean by at least 1 standard deviationis 0.1587.
Explanation of Solution
Calculation:
Empirical Rule:
The Empirical Rule for a Normal model states that:
- • Within 1 standard deviation of mean, 68.26% of all observations will lie.
- • Within 2 standard deviations of mean, 95.44% of all observations will lie.
- • Within 3 standard deviations of mean, 99.73% of all observations will lie.
Consider the property regarding 1 standard deviation difference from mean of theEmpirical Rule. It indicates that:
Hence, the probability that the length of a brook trout exceeds the mean by at least 1 standard deviationis 0.1587.
c.
Find the probability that the length of a brook trout exceeds the mean by at least 2 standard deviations.
Answer to Problem 76CE
Theprobability that the length of a brook trout exceeds the mean by at least 2 standard deviations is 0.0228.
Explanation of Solution
Calculation:
Consider the property regarding 2 standard deviations difference from mean of theEmpirical Rule. It indicates that:
Hence, the probability that the length of a brook trout exceeds the mean by at least 2 standard deviations is 0.0228.
d.
Find the probability that the length of a brook trout is within 2 standard deviations of the mean.
Answer to Problem 76CE
Theprobability that the length of a brook trout is within2 standard deviations of the mean is 0.9544.
Explanation of Solution
Calculation:
Consider the property regarding 2 standard deviations difference from mean of theEmpirical Rule. It indicates that:
Hence, the probability that the length of a brook trout is within 2 standard deviations of the mean is 0.9544.
Want to see more full solutions like this?
Chapter 7 Solutions
Loose-leaf For Applied Statistics In Business And Economics
- MATLAB: An Introduction with ApplicationsStatisticsISBN:9781119256830Author:Amos GilatPublisher:John Wiley & Sons IncProbability and Statistics for Engineering and th...StatisticsISBN:9781305251809Author:Jay L. DevorePublisher:Cengage LearningStatistics for The Behavioral Sciences (MindTap C...StatisticsISBN:9781305504912Author:Frederick J Gravetter, Larry B. WallnauPublisher:Cengage Learning
- Elementary Statistics: Picturing the World (7th E...StatisticsISBN:9780134683416Author:Ron Larson, Betsy FarberPublisher:PEARSONThe Basic Practice of StatisticsStatisticsISBN:9781319042578Author:David S. Moore, William I. Notz, Michael A. FlignerPublisher:W. H. FreemanIntroduction to the Practice of StatisticsStatisticsISBN:9781319013387Author:David S. Moore, George P. McCabe, Bruce A. CraigPublisher:W. H. Freeman