Why is this important? Requirement Understand research articles Do research for yourself Real world Develops your analytical and critical thinking

Statistics

Descriptive Statistics

Practice Based on a sample of participants, it appears that a new drug will be effective at stopping headaches The enrollment in this course as of August 15th was 22

Practice On your first test you received a score of 84 out of 100 Markey will likely be the next president; of the 100 people surveyed 82% said they would vote for him

Inferential Statistics Problem: Is that going to be the exact answer? Chance influences the sample –“true” variation –“error” variation Sample = “true” + “error”

Basic Terms Population –Consists of all the scores of some group Sample –Is a subset of a population

Basic Terms Parameters –A numerical or nominal characteristic of a population Statistics –A numerical or nominal characteristic of a sample Statistics change from one sample to the next -- Parameters are constant!!

Basic Terms Variable –Something that exists at more than one amount Quantitative Variable –A score attached to a variable -- tells you something about its amount

Quantitative Variable

Quantitative Variable to 150.5

Quantitative Variable

Quantitative Variable 51.5 to

Quantitative Variable

Quantitative Variable to

Quantitative Variable To find lower limit score: –Subtract half the unit of measurement from the score For 48.6 the unit of measurement is 0.1 Half of 0.1 is = 48.55

Quantitative Variable To find upper limit score: –Add half the unit of measurement from the score For 48.6 the unit of measurement is = 48.65

Qualitative Variable Are not continuous like quantitative variables They are usually words or names –e.g., gender, political party, religion

Practice 14, average number of minutes before a student falls asleep 4000, this course number 3.5, a students GPA

Practice , Ned Flanders phone number 1,301, the average weight of the human brain in grams

Sample Cookbook Page To find a quantitative numbers upper and lower limits 1) Determine the unit of measurement Example: 14 = = =.01

Sample Cookbook Page 2) Calculate half the unit of measurement Example: 1 =.5.1 = =.005

Sample Cookbook Page 3) To find upper limit add half the unit of measurement to the original number 4) To find lower limit subtract half the unit of measurement to the original number

Sample Cookbook Page Examples: 12 = to = to = to

The meaning of numbers 90 The number correct on a test out of 100 The last two digits of your SSN The percentile you scored on the SAT

Nominal Scale Are not really scales at all They do not scale items along any dimension, but rather label them Numbers are used as names and have no quantitative value

Nominal Scales Gender Political party Your SSN Religion

Ordinal Scales Has the characteristics of the nominal scale PLUS: the characteristic of indicating greater than or less than –i.e., RANK ORDER

Ordinal Scales Rank of professor Your place in a foot race Saying “This class is smaller then my other class”

Interval Scales Has the properties of BOTH the nominal and ordinal scales PLUS: the intervals between the numbers are equal –e.g., the distance between 4 and 5 is the same distance between 1 and 2

Interval Scales Temperature –the difference between 10 o F and 20 o F is the same as the difference between 80 o F and 90 o F Problem: What does 0 o F mean? With interval scales you CAN NOT make ratio statements

Interval Scale Appears twice as large

Interval Scale Now it appears three-times as large!

Ratio Scales Has all the characteristics of the nominal, ordinal, and intervals scales PLUS: it has a true zero point This zero point indicates a complete absence of the thing measured

Ratio Weight Height Speed Distance

Features of the four scales

Why are the types of scales important? They help you understand what type of statistic to use

Practice Inches on a yardstick Drivers licenses number Dollars as a measure of income Order of finish in a car race Intelligence test scores