stats CHAPTER 1.docx

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22 Apr 2012

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2 General Purposes of Statistics
i) Used to organize and summarize information so that the results can be communicated
ii) Help to answer the questions that initiated the research by determining exactly what conclusions
are justified based on the results that were obtained
Statistics: refers to a set of mathematical procedures for organizing, summarizing and interpreting
Population: the set of all the individuals of interest in a particular study
Sample: a set of individuals selected from a population, usually intended to represent the population in
a research study
Parameter: a characteristic that describes a population; a value, usually, numerical, that describes a
population. A parameter may be obtained from a single measurement, or it may be derived from a set
of measurements from a population --- typically every population parameter has a corresponding
sample statistic
Sample Statistic: a characteristic that describes a sample
Data: are measurements or observations.
Data Set: is a collection of measurement or observations
Datum: is a single measurement or observation and is commonly called a score or raw score
a) Descriptive Statistics
- Consists of statistical procedures that are used to simplify and summarize data
- Scores are often organized in a table or a graph so that entire set of scores can be seen
b) Inferential Statistics
- Summarizes a set of scores by computing an average a single descriptive value for the
entire set
- Purpose of inferential statistics is to use sample data to reach general conclusions about
Techniques that allow us to study samples and then make generalizations about the population from
which they were obtained
However a sample provides only limited information about the population there is usually some
discrepancy between a sample statistic and corresponding population parameter
Sampling Error: the discrepancy, or amount of error, that exists between a sample statistic and the
corresponding population parameter
- Sample statistics vary from one sample to another and typically are different from the
corresponding population parameters
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