8 - measure metabolic rates in calories both the mean and...

Info icon This preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
The interquartile range IQR is the distance between the first and third quartiles, IQR = Q3 − Q1 Call an observation a suspected outlier if it falls more than 1.5 × IQR above the third quartile or below the first quartile. Standard deviation: Measure of the spread about the mean of a distribution. It is an average of the squares of the deviations of the observations from their mean, also equal to the square root of the variance. Variance: Measure of the spread about the mean of a distribution. Equal to the standard deviation squared. The number n – 1 is called the degrees of freedom of the variance or standard deviation. * s measures spread about the mean and should be used only when the mean is chosen as the measure of center. * s is always zero or greater than zero. s = 0 only when there is no spread. This happens only when all observations have the same value. Otherwise, s > 0. As the observations become more spread out about their mean, s gets larger. * s has the same units of measurement as the original observations. For example, if you
Image of page 1
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: measure metabolic rates in calories, both the mean and the standard deviation s are also in calories. This is one reason to prefer s to the variance s2, which is in squared calories. * Like the mean, s is not resistant. A few outliers can make s very large. The five-number summary is usually better than the mean and standard deviation for describing a skewed distribution or a distribution with strong outliers. Use and s only for reasonably symmetric distributions that are free of outliers. A graph gives the best overall picture of a distribution. Numerical measures of center and spread report specific facts about a distribution, but they do not describe its entire shape. Numerical summaries do not disclose the presence of multiple peaks or clusters. This symbol for population standard deviation is (o ? ? ? ? ? ) which is pronounced "sigma". "s" is the symbol for sample standard deviation....
View Full Document

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern