What is Statistics. Chapter 1. GOALS. What is meant by statistics? Understand why we study statistics. Explain what is meant by descriptive statistics and inferential statistics. Distinguish between a qualitative variable and a quantitative variable.
Statisticsis the science of collecting, organizing, presenting, analyzing, and interpreting numerical data to assist in making more effective decisions.
Statistical techniques are used extensively by marketing, accounting, quality control, consumers, professional sports people, hospital administrators, educators, politicians, physicians, etc...
Descriptive Statistics - methods of organizing, summarizing, and presenting data in an informative way.
EXAMPLE 2: According to Consumer Reports, General Electric washing machine owners reported 9 problems per 100 machines during 2001. The statistic 9 describes the number of problems out of every 100 machines.
EXAMPLE 3: Pie Chart (chapter 2) For Running Shoes Sold At Big 5 Sports
EXAMPLE 4: Frequency Distribution (chapter 2)
A populationis a collection of all possible individuals, objects, or measurements of interest.
A sample is a portion, or part, of the population of interestPopulation versus Sample
Example 1: TV networks constantly monitor the popularity of their programs by hiring Nielsen and other organizations to sample the preferences of TV viewers.
Example 3: The accounting department of a large firm will select a sample of the invoices to check for accuracy for all the invoices of the company.Inferential Statistics
Continuous variable can assume any value within a specified range.
EXAMPLE: The pressure in a tire, the weight of a pork chop, or the height of students in a class.
Usually is measured (accuracy depends on measuring instrument)
Money is often categorized as a continuous variable (even though you can’t count between pennies)
During a taste test of 4 soft drinks, Coca Cola was ranked number 1, Dr. Pepper number 2, Pepsi number 3, and Root Beer number 4.
One category is higher than another (Ordered).
There is a constant unit of measurement.
Zero is just a point on the scale; or there is no natural zero point.
Division of two numbers does not make sense.
Scale or rank are good examples
EXAMPLE: Temperature on the Fahrenheit scale.
Zero is just a point on the scale.
EXAMPLE: Shoe size and dress size.
There is no natural zero point
EXAMPLE: Years in which Whole Foods Market Inc. stock split.
Division of 1992 and 1993 does not make sense.
EXAMPLES: Rank of Indi 500 results, Test scores.Interval Level
Levels of Data
Data may only
Data are ranked
Meaningful 0 point