Scales of Measurement - Lecture Notes Ch.1

Scales of Measurement • Nominal - label and categorize - no quantitative distinctions → Exampie: gender, diagnosis, experimental or contros • Ordinal - Categorizes oloservatons • Interval - Ordered categories - interval between categories of equal ste - arbitrary or alosent Zero point → Example: temperature, 1Q, gorf scores (albove/berow par) • Ratio - ordered categories - equal interval between categories - alsolute zero point → Example: number of correct answers, time to compere task, goin in height since last year Levels of measurement Determine the measurement level. Letter Grade GRE Score Yes Yes Yes Yes No Temperature (F) • Learning Спеск A study assesses the optimal size (number of other members) for Study groups The varialole "size of group" iS ... a) discrete and interval b) continuous and ordinal C) discrete and ratio d) continuous and interval Data Structures • Data Structure 1: descriptive research • One cor more) variables measured per individual - "Statistics" describe the observed variable - may use category ard/or numerical variables • Data Structures 2: the Correlational method - one group of participants - measurement of 2 variabies for each participant - goal is to describe type and magnitude of the relationship - patterns in the data reveal relationships - non• experimental method of study Data structunes for studies evaluating the resconstip cerasen valdoes Correlational Method Limitations • Can demonstrate the existence of a relationship *does not provide an explanation for the relationship • most importantly, does not demonstrate a cause -and-effect relationship between the 2 variables Data Structures • Data Structures 3: Comparing 2 (or more) groups of Scores - one variable defines the groups - Scores are measured on Second variable - both experimental and non-experimental Studies use this Structure Data structure for studies comparing groups Experimental Method • Goal of experimental method - to demonstrate a cause-and-effect relationship • Manipulation - the level of one variable is determined by the experimenter • Control rules out influence of other variables - participant variables - environmental variabies Independent / Dependent Variables • Independent variable is the variaoe manipulated by the restarcher - independent becaure no other variate in the Study influences is value • Dependent variabe is tue one observed to assess the effect of treatment - dependent because its value is thought to depend on the vaiue of tue independent variable Experimental Method: Cantrol • methods of control - random assignment of subjects - matching of Subiects - holding level of Some potentially infivential variakes Constant • Control Condition - individuals do not receive the experimental treatment - they either receive no treatment or they receive a neutral, placebo treadment - purpose: to provide a baseline for comparison with the experimental condition • Experimental Condition - individuals do receive tue experimental treatment Non- Experimental Methods • Non-equivalent groups - researcher compares groups - researcher Cannot Control wns goes into wnich group • Pre-test / Pro-test - individuals measured at 2 pants in time - researcher cannot control influence of the passage of time • Independent variable is quasi- independent Learning Check Decide if each of the following statements is true or faise. all research methods have an independent variable all research methods can snow Cause-and-effect relationships Statistical Notation • Statistics uses operations and notation you have already learned - Appendix A has a mathematical review • Statistics also uses some specific notation - Scores are referred to as x (andY) - N is tue number of Scores in a population - n is te number of scores in a sample Summation Notation • many Statistical procedures involve summing (adding up) a set of Scores • the Summation Sign I stands for Summation - the E is followed by a symbol or equation that defines wnat is to be summed - Summation is done after operations in parentheses, squaring, and multiplication or division - Summation is done before other adition or Subtraction