Mid Term Review

# Mid Term Review - Practice of Statistics Define Statistics...

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Fall 2008 1 Practice of Statistics Define Statistics The science of statistics is Collecting Organizing Summarizing Analyzing … information to draw conclusions or answer questions.

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Fall 2008 2 Practice of Statistics Understanding the Process of Statistics A population Is the group to be studied Includes all of the individuals in the group A sample Is a subset of the population Is often used in analyses because getting access to the entire population is impractical
Fall 2008 3 Practice of Statistics Distinguishing Between Qualitative and Quantitative Variables Characteristics of the individuals under study are called variables Some variables have values that are attributes or characteristics … those are called qualitative or categorical variables Some variables have values that are numeric measurements … those are called quantitative variables The suggested approaches to analyzing problems vary by the type of variable

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Fall 2008 4 Practice of Statistics Distinguishing Between Qualitative and Quantitative Variables Examples of qualitative variables : Gender, Zip code, Blood type, States in the United States Qualitative variables have category values … those values cannot be added, subtracted, etc. Examples of quantitative variables : Temperature, Sales of a product, Number of children in a family Quantitative variables have numeric values … those values can be added, subtracted, etc.
Fall 2008 5 Practice of Statistics Distinguishing between Discrete and Continuous Variables Quantitative variables can be either discrete or continuous Discrete variables Variables that have a finite or a countable number of possibilities Often these variables are counts Continuous variables Variables that have an infinite, not countable, number of possibilities Often these variables are measurements

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Fall 2008 6 Obtaining a Simple Random Sample Usually only a part of the population can be analyzed A simple random sample is when every possible sample of size n out of a population of N has an equally likely chance of occurring Examples For a simple random sample of size n = 2 from a population size of N = 4, each of the 6 possible samples has an equally likely chance of occurring
Organizing Qualitative Data Constructing a Frequency Distribution Qualitative data values can be organized by a frequency distribution A frequency distribution is a table that lists Each of the categories The frequency, or the count, for each category Fall 2008 7

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Organizing Qualitative Data Constructing a Relative Frequency Distribution The frequencies are the counts of the observations The relative frequencies are the proportions (or percents) of the observations out of the total A relative frequency distribution lists Each of the categories The relative frequency for each category Fall 2008 8
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## This note was uploaded on 10/15/2008 for the course STAT 250 taught by Professor Sims during the Fall '08 term at George Mason.

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Mid Term Review - Practice of Statistics Define Statistics...

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