Psych 243 1st Edition Lecture 3 Outline of Last Lecture I. Why do scientists use statistics?II. Correlational studyIII. Correlation does not mean causationIV. Characteristics of experimental studiesV. Types of variables VI. Quasi-independent variablesVII. Four types of measurement scalesVIII. Continuous vs. discrete scalesOutline of Current Lecture I. Classification of Variablesa. Broad Classification of Variablesb. 4 Types of Measurement Scales (more classification)c. Why does any of this matter? II. Frequencya. Describing a single variableb. Rfc. Frequency Distributiond. Displaying Frequency information in a graphCurrent LectureClassification of VariablesBroad Classification of Variables- Quantitative: Specifies an amount e.g. Age/GPA- Qualitative: specifies a category e.g. Gender, eye color, major4 Types of Measurement Scales- Nominal= nameo Differ only in kind (different categories) gender, religion, political affiliationo Can’t order the valueso Assigning numbers doesn’t mean an amount of something SS#, football jersey- Ordinal= ordero Ranking e.g. sports standing, class rankThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o Can’t make assumption about degree of difference e.g. difference between gold & silver medals not recognized- Intervalo Ordered categories of the same sizeo Equal space between intervalo No real “0” as origin of the score or it is arbitraryo E.g. temperature or psychological scales (IQ)- Ratioo Intervals are equally spaced o Have a real “0”o Quantitative height, weight, exam scoreWhy does any of this matter?- The type of statistical procedure that you do depend on the variables that you studyAnswers to last lecture’s in-class question- Sex Nominal- Major Nominal- Amount of shoes Ratio- Books read for funRatio- Hours of sleep each night Ratio- Amount of hours spent studying Ratio- GPA Complicated answer, can be anything BUT NOMINAL ***will not be on exams***- Amount of time in last relationship Ratio- Scale of 1-7 how likely will you be in sorority Interval- Scale of 1-7 how much do you like Bing Interval- Order the factors that affected your college decision OrdinalFrequencyDescribing a Single Variable- Q1: How many scores are in a sample?o A: Count them!o N: total number of scores- Q2: How many times did these values occur? o A: Construct a frequency tableo f= frequency the number of times a particular value of your variable occursrf- Relative Frequency: the proportion of the total N made up by a score’s simple frequencyo Rf= f/n- Cumulative frequency= cf: the sum of all the frequencies of all the scores at or below a particular score- Relative cumulative frequency= rel. cf: The sum of all the relative frequencies at or below a particular scoreFrequency Distribution- Histogram, Frequency Polygon, Bar Graph & Pie grapho You decide the graph based on the frequency distributionDisplaying Frequency Information in a graph- Histogram small range of Interval/Ratio data- Frequency Polygon large range of Interval/Ratio data- Bar Graph Nominal/Ordinal data- Pie Graph Sometimes* used for nominal