Sampling and Data: Summary 1.4 2008/04/09 14:07:51 GMT-5 2008/04/29 15:00:01.190 GMT-5 Barbara Illowsky cnx@cnx.org Susan Dean cnx@cnx.org Jonathan Emmons jemmons.public@gmail.com Uchenna Kevin Anyikam projects@southwoodmm.com Connexions cnx@cnx.org cluster continuous convenience cumulative data discrete frequency parameter population probability qualitative quantitative random relative replacement sample sampling simple statistic statistics stratified systematic variable This module provides an outline/review of key concepts related to statistical sampling and data. Note: This module is currently under revision, and its content is subject to change. This module is being prepared as part of a statistics textbook that will be available for the Fall 2008 semester.

Statistics Deals with the collection, analysis, interpretation, and presentation of data

Probability Mathematical tool used to study randomness

Key Terms Population Parameter Sample Statistic Variable Data

Types of Data Quantitative a number Discrete (You count it) Continuous (You measure it) Qualitative A category (words)

Sampling with Replacement A member of the population may be chosen more than once

Sampling without Replacement A member of the population may be chosen only once

Random Sampling Each member of the population has an equal chance of being selected

Sampling Methods Random Simple random sample Stratified sample Cluster sample Systematic sample Not Random Convenience Sample Samples must be representative of the population from which they come. They must have the same characteristics. However, they may vary but still represent the same population

Frequency, Relative Frequency, and Cumulative Relative Frequency Frequency (freq. or F) The number of times an answer occurs Relative Frequency (rel. freq. or RF) The proportion of times an answer occurs Can be interpreted as a fraction, decimal, or percent Cumulative Relative Frequencies (cum. rel. freq. or cum RF) An accumulation of the previous relative frequencies