AN INTRODUCTION TO STATISTICS WHAT DOES A STATISTICIAN

AN INTRODUCTION TO STATISTICS

WHAT DOES A STATISTICIAN DO? A statistician makes sense of information collected about the world ● Analyze effectiveness of drug treatments ● Determining behavior patterns ● Analyze spread of West Nile Virus ● Analyze performance of individuals, businesses, stocks, etc.

WHAT IS STATISTICS? Statistics is a branch of mathematics dealing with the collection, analysis, interpretation, and presentation of masses of numerical/categorical data.

WHAT IS STATISTICS? Statistics is a way of reasoning together with collection tools and methods designed to help us to understand data and information about the world.

WHAT ARE STATISTICS? ● Calculations made from data.

WHAT ARE DATA? ● Systematically recorded information together with context

CONTEXT Tells: ● ● ● Who was measured What was measured Where data was collected When data was collected Why study was performed How data was collected

DATA CAN BE. . . ● ● Numbers Dates Words Codes or other labels

What is univariate data? one variable • the major purpose of univariate analysis is to describe one variable • central tendency: mean, mode, median • variability: range, max, min, quartiles, standard deviation • graphs: histogram, box-and-whisker plot

What type of data is it? Qualitative vs. Quantitative • Deals with descriptions. • Deals with numbers. • Data can be observed but not measured. • Data that can be measured. • Colors, textures, smells, tastes, appearance, beauty, etc. • Length, height, area, volume, weight, speed, time, temperature, cost, ages, etc.

QUALITATIVE (CATEGORICAL) VARIABLE ● Is a classification or categorization ○ Something that is a name, word, or code ● Examples: ○ ○ Name of country Type of shoe Class year Area code

QUANTITATIVE VARIABLE ● Is a measurement, amount, or count ○ Can by indicated by words “amount” or “number of” ● Examples: ○ ○ Height Amount of time spent studying Distance traveled Amounted of money in your wallet

ORDINAL VARIABLE ● Is an ordered rating or ranking ● Examples: ○ Course grade ○ Class rank ○ Customer service rating

CAUTION! A thing is not a variable. Shoes are things. The type of shoes is a qualitative variable. The number of shoes is a quantitative variable.

QUANTITATIVE VARIABLES Quantitative variables can be discrete or continuous.

DISCRETE QUANTITATIVE VARIABLES ● A quantitative variable is discrete if the variable involves a count (no decimals/fractions). ● Examples: ○ Number of students ○ Number of shoes ○ Number of bills in your wallet

CONTINUOUS QUANTITATIVE VARIABLES ● A quantitative variable is continuous if the variable involves a measurement. ● Examples: ○ Height ○ Distance traveled ○ Weight of a box

CAUTION! ● Important to consider what values mean and how they are being used ● Do not treat all numerical data as quantitative ○ The average of qualitative data is meaningless (example: the average zip code)

Example 1: Quantitative or Qualitative? • Number of students in a class who turn in a project before it is due. • Gender of the next baby born at a hospital. • Amount of fluid ounces dispersed by a soda machine. • Thickness of the gelatin coating on a pill. • Birth order (oldest, middle, youngest) of a student.

Homework • Pick 10 items in your home. • Describe 5 of these items quantitatively. Provide three different descriptors for each item. • Describe the other 5 items qualitatively. Provided three different descriptors for each item. • This will be collected for a homework grade tomorrow.