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Learn how statistics scales categorize data for accurate analysis and decision-making. Discover nominal, ordinal, interval, and ratio scales through practical examples and understand their significance in statistical research.
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Why is this important? • Requirement • Understand research articles • Do research for yourself • Real world
The Three Goals of this Course • 1) Teach “factoids” • 2) Teach a new way of thinking • 3) Self-Confidence in statistics
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 December 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”
The meaning of numbers 90 • The number correct on a test out of 100 • The last two digits of your SSN • Your place in a race with 100 participants • Your place in the Boston Marathon • The percentile you scored on the GRE
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 10o F and 20o F is the same as the difference between 80o F and 90o F • Problem: What does 0o F mean? • With interval scales you CAN NOT make ratio statements
Interval Scale 50 70 10 30 80 0 20 40 60 Appears twice as large
Interval Scale 30 50 -10 10 0 60 -20 20 40 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
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
1) Is depressed, blue 2) Is not relaxed, does not handle stress well 3) Can be tense
4) Worries a lot 5) Is easily upset
Neuroticism Raw Score • Add your answers • Your score can range between 5- 25 • What does your score mean? • Note: It is meaningless unless you know how others scored
Simple Frequency Distribution 1) Find the highest and lowest scores 2) Write in descending order all the numbers from 24 to 6
Simple Frequency Distribution 3) Start with the number in the upper-left corner, draw a line under it, and place a tally mark in the frequency distribution 4) Do this with all the data 5) Count the number a tally marks
Group Frequency Distribution • Scores are grouped into equal-sized ranges called “class intervals” • Usually want around 10 class intervals
Graphic Presentation of Data • Basic parts of a graph Y axis X axis
Histogram • Graphs quantitative data • Neuroticism data