CHAPTER 1

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

information

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

2 STATISTICAL PROCEDURES TO ORGANIZE AND INTERPRET DATA

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

populations

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