Stat 281: Introduction to Probability and Statistics A prisoner had just been sentenced for a heinous crime and was returned to his cell. An inquisitive guard could not wait to ask him about the outcome. Guard: “What did you get for a sentence?” Prisoner: “I could choose life or 100 years.” Guard: “And what did you choose?” Prisoner: “Well, life, obviously. Statistically speaking, that is the shorter sentence.”

I need from:  Missing or invalid addresses: –Beardt, Bradley S. –Coulter, David P. –Jacobson, Michael H. –Keating, Maxon J. –Magnuson, Melissa L.  Anyone else who did not receive an from me (about the room change)

and web page  My and web page are on the syllabus  If you have campus , just type “Dwight Galster” and it should come up  Otherwise it is  My web page is  Once at the web page click on the course in the schedule to get to the course page.  PowerPoints and assignments will be posted on the web page  I suggest you bookmark the course page and visit it often.

Keys to Success  Definitions are crucial in stats class. If you don’t know the precise meaning of a word, the whole point of the sentence/paragraph/chapter could be lost!  Concepts are important in stats class. –Lots of formulas—don’t plug in numbers blindly—understand why –Review and integrate

Definitions  Data (is/are?)  Population (of? Not a number) Finite/Infinite/Practically Infinite  Sample (proper subset, finite)  Variable (response, random)  Parameter/Statistic Greek/Latin  Experiment/Observational Study

Probability vs. Statistics  Probability: Properties of population are known. Make predictions about sample.  Statistics: Sample is known. Guess (estimate) properties of population.  Statistics (is/are?) –Descriptive –Inferential

Types of Data (Variables)  Categorical (Class, Attribute, Qualitative)  Numeric (Quantitative) –Discrete (Finite or Infinite) –Continuous (always Infinite)  Measurement Scales –Nominal –Ordinal –Interval –Ratio

Identify the Data Types 1.The daily high temperature (°F) in Brookings. 2.The make of automobile driven by each student. 3.The defect status of 9 volt batteries being tested. 4.The weight of a lead pencil. 5.The length of time billed for a long distance call. 6.Which brand of cereal children eat for breakfast. 7.The genre of a book checked out of the library. 8.The time until a pain reliever begins to work.

Variation  No matter what the response variable: there will always be variability in the data.  One of the primary objectives of statistics: measuring and characterizing variability.  Controlling (or reducing) variability in a manufacturing process: statistical process control.

Are you above average?  The vast majority of people have more than the average number of legs.  “When she told me I was average, she was just being mean.”  You know how dumb the average person is? Well, half the population is dumber than that!

Sampling Methods  Sampling Frame  Representative  Biased and Unbiased  Sampling Methods –Convenience –Volunteer –Judgment –Probability

Probability Sample Designs  Simple Random Sample  Systematic Sample  Stratified –Proportional (Quota)  Cluster