Chapter_9 - Chapter 9: Gathering and Measuring Information...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 9: Gathering and Measuring Information October 11, 2011
Background image of page 1

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

View Full DocumentRight Arrow Icon
Descriptive Statistics: Terms to Know Unit of observation: what or who is being described or analyzed or entity under study. It can be an event, person, or an object. Data points: individual observations that collectively make up the data we are trying to describe.
Background image of page 2
Descriptive Statistics: The Mean and the Median The mean or average is the sum of a set of numbers divided by the number of observations (also called n). The median is the midpoint in a distribution of numbers when you organize them from smallest to largest. Deciles, quartiles, and percentiles are ways to describe where an observation falls in a range of observations.
Background image of page 3

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

View Full DocumentRight Arrow Icon
Examples of Mean, Median, and Percentiles Percentiles -Over 50% of the students studied less than 2 hours. Hrs Studied Student 1 0 Student 2 1 Mean is 28/10 2.80 Student 3 1 Median 2 Student 4 2 Student 5 2 Student 6 2 Student 7 3 Student 8 3 Student 9 4 Student 10 10 Sum of Hrs 28
Background image of page 4
How do I know whether to use the mean or median? What is an outlier? A data point that lies far from the rest of the distribution. Outliers affect the mean but not the median. For example, in my Politics of Poverty class, one of student’s has a dad that makes $750,000! That is an outlier compared to the class average of about $125,000.
Background image of page 5

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

View Full DocumentRight Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 11/16/2011 for the course POLI SCI 2070 taught by Professor Davis during the Fall '11 term at LSU.

Page1 / 27

Chapter_9 - Chapter 9: Gathering and Measuring Information...

This preview shows document pages 1 - 6. Sign up to view the full document.

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