L05-09 - The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL...

Info iconThis preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon
9/10/09 Lecture 5 1 STOR 155 Introductory Statistics Lecture 5: Density Curves and Normal Distributions (I) The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
9/10/09 Lecture 5 2 A problem about Standard Deviation A variable has 5 possible values. The mean is 125 and the standard deviation is 25. If a sixth number of 125 is added in, what is the new standard deviation?
Background image of page 2
9/10/09 Lecture 5 3 To describe distribution of variable X • Plot your data: – Stemplot, histogram, boxplot • Look for overall pattern (shapes) + striking deviations (outliers) • Calculate appropriate numerical summaries about center and spread – Mean, median, mode – Range, percentiles, quartiles, standard deviation – Five-number summary, boxplot – IQR and outliers Make things easier with a smooth curve
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
9/10/09 Lecture 5 4
Background image of page 4
9/10/09 Lecture 5 5 Density Curve --- A Math Approximation • To calculate probabilities, we define a probability density function f(x) . • The curve that plots f(x) is called the corresponding density curve . f(x) satisfies: -- f(x) >= 0; – The total area under the curve representing f(x) equals 1.
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
9/10/09 Lecture 5 6 Density Curves • Describe the overall shape of distributions • Idealized mathematical models for distributions • Show patterns that are accurate enough for practical purposes • Always on or above the horizontal axis • The total area under the curve is exactly 1 • Areas under the curve represent relative frequencies of observations
Background image of page 6
9/10/09 Lecture 5 7
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 8
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 11/17/2011 for the course STOR 155 taught by Professor Andrewb.nobel during the Fall '08 term at UNC.

Page1 / 27

L05-09 - The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL...

This preview shows document pages 1 - 8. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online