2011-Psych 60-Lecture 2

2011-Psych 60-Lecture 2 - 3/30/11 Announcements My Email:...

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Unformatted text preview: 3/30/11 Announcements My Email: jlparris@ucsd.edu First homework assignment available this aCernoon (due by Monday at 11am) Tutorial available on WebCT Today StaKsKcs as a discipline Basic Terminology Measurement 1 3/30/11 100 years ago the world's populaKon was 25% of what it is now Facebook has more than 600 million acKve users The average GPA of UCSD undergraduates for Fall 2009 was 3.04 2 3/30/11 A "StaKsKc" Any func%on of data A "StaKsKc" Any func%on of data A "StaKsKc" Any func%on of data A "StaKsKc" Any func%on of data ProporKon, Sum, Average, Minimum, Maximum Useful to represent some aspect of the data in a simple, easy to understand way Is defined by an operaKon on data 3 3/30/11 "StaKsKcs" A set of mathemaKcal procedures for organizing, summarizing, and interpreKng informaKon Prac%cal math Branches of StaKsKcs DescripKve StaKsKcs InferenKal StaKsKcs DescripKve StaKsKc InferenKal StaKsKc StaKsKcal procedures to summarize, organize, and simplify the communicaKon of data StaKsKcal techniques that facilitate inferences about populaKons from data collected in samples Obama received 53.4% of the vote in the 2008 PresidenKal ElecKon 66,882,230 votes out of 125,225,901 votes Obama is predicted to receive 55% of the vote in the 2008 PresidenKal ElecKon, 2.1% Gallup Poll of 2472 voters, 11/2/08 4 3/30/11 Terminology "Data" Data (plural) are measurements or observaKons Data set: collecKon of measurements or observaKons Datum (singular): is a single measurement or observaKon, aka. Score, or raw score "Variable" a characterisKc or condiKon that changes or has different values for different individuals Age, Gender, Height, Facebook user or not 5 3/30/11 Variables "PopulaKon" A populaKon is the set of all individuals (units) of interest Plankton in the ocean, People in the world, People at UCSD, Dogs in San Diego 6 3/30/11 "Sample" A sample is a set of individuals (units) selected from a populaKon Parameters and StaKsKcs PopulaKon Sample Average Sum Maximum score Usually intended to "represent" the populaKon Usually much smaller than populaKon Average Sum Maximum score STATISTICS PARAMETERS Parameters and StaKsKcs Parameter: a value (usually numeric) that describes a populaKon StaKsKc: a value (usually numeric) that describes a sample PopulaKon 260- Psych 60 students PopulaKon Parameters Average Age: 19.8 Average IQ: 110.5 70% Female, 30% Male Sample 2 Jake Laura Tiffany Sarah Ann Sample 1 Mike Tom Jennifer Andy Lucy Sample 1 Sta%s%cs Average Age: 21.8 Average IQ: 106.2 40% Female, 60% Male Sample 2 Sta%s%cs Average Age: 19.2 Average IQ: 112.2 80% Female, 20% Male 7 3/30/11 Sampling Error PopulaKon Parameters Average Age: 19.8 Average IQ: 110.5 70% Female, 30% Male Sample 1 Sta%s%cs Average Age: 21.8 Average IQ: 106.2 40% Female, 60% Male Sample 2 Sta%s%cs Average Age: 19.2 Average IQ: 112.2 80% Female, 20% Male Sampling Error Sampling Error 8 3/30/11 Sampling Error The discrepancy (or amount of error) that exists between a sample staKsKc and the corresponding populaKon parameter PopulaKon All UCSD Students Two Possible Explana0ons: 1. There is no effect of caffeine on test scores and the 4-point difference is due to sampling error 2. There is a real effect of caffeine on test performance No Caffeine Group Group 2 Sta%s%cs n = 50 82, 77 79, Average test score: 79 64, 81, 92, 74, 88, 91, 81, 79, 70... Caffeine Group n = 50 86, 76, 89, 91, 78, 89, 67, 54, 67, 88, 75, 90... Group 1 Sta%s%cs Average test score: 75 Measurement 9 3/30/11 Measurement Construct The process of assigning numbers or labels to physical phenomena according to a rule Internal anributes or characterisKcs that cannot be directly observed OperaKonal DefiniKon A procedure for measuring an external behavior so that those measurements may be used to infer about the status of the underlying construct what is measured is not the construct, but rather something physical we choose to believe indexes the presence or quan0ty of the construct 10 3/30/11 Measurement Types Discrete vs. Con%nuous Discrete vs. ConKnuous Discrete variables consists of separate categories where no values exist between neighboring categories (e.g. gender, number of children, whole-number age in years) ConKnuous variables have a (theoreKcally) infinite number of values falling between any two observed values (e.g. actual age in years, distance, Kme) 11 3/30/11 Measurement Scales Measurement Scales Nominal Ordinal Interval/RaKo Nominal Ordinal Interval/RaKo Physical World Anribute of Interest a nominal scale consists of a set of categories that have different names. an ordinal scale consists of a set of categories that are organized in an ordered sequence e.g. gender, poli%cal ideology e.g. finishing place in race, Clothing sizes (S,M,L,XL) Olympic medals interval and ra%o scales consists of a series of ordered categories where the categories form intervals of the same size. Ra%o scales have a meaningful zero point e.g. distance, weight, temperature* 12 3/30/11 Physical World Anribute of Interest (biological sex) Physical World Anribute of Interest (biological sex) Physical World "MALE" Anribute of Interest (biological sex) Physical World "MALE" Anribute of Interest (biological sex) "FEMALE" "FEMALE" 13 3/30/11 Physical World "MALE" Anribute of Interest (biological sex) Physical World "MALE" Anribute of Interest (biological sex) "MALE" "FEMALE" "FEMALE" "FEMALE" Nominal "MALE" "FEMALE" Physical World Anribute of Interest (amount of fabric) 14 3/30/11 Physical World Anribute of Interest (amount of fabric) Most Fabric Physical World Anribute of Interest (amount of fabric) Most Fabric Least Fabric Least Fabric Physical World Anribute of Interest (amount of fabric) Most Fabric Physical World Anribute of Interest (amount of fabric) Most Fabric L L M M S Least Fabric S Least Fabric 15 3/30/11 Physical World Anribute of Interest (amount of fabric) Most Fabric Physical World Anribute of Interest (amount of fabric) Most Fabric L L M M S Least Fabric S Least Fabric Physical World Anribute of Interest (amount of fabric) Most Fabric Physical World Anribute of Interest (amount of fabric) Most Fabric L L Ordinal M M S Least Fabric S Least Fabric 16 3/30/11 Physical World Anribute of Interest (%me to finish race) Shortest Time Longest Time Physical World Anribute of Interest (%me to finish race) Shortest Time Physical World Anribute of Interest (%me to finish race) Shortest Time 1st Place 1st Place 2nd Place 2nd Place 3rd Place Longest Time 3rd Place Longest Time 17 3/30/11 Physical World Anribute of Interest (%me to finish race) Shortest Time Physical World Anribute of Interest (%me to finish race) Shortest Time 1st Place 1st Place Ordinal 2nd Place 2nd Place 3rd Place Longest Time 3rd Place Longest Time Physical World Anribute of Interest (Extent in Space) 18 3/30/11 Physical World Anribute of Interest (Extent in Space) Infinite Extent in Space Physical World Anribute of Interest (Extent in Space) Infinite Extent in Space No Extent in Space No Extent in Space Physical World Anribute of Interest (Extent in Space) Infinite Extent in Space Physical World Anribute of Interest (Extent in Space) Infinite Extent in Space 72" 72" 66" 66" 60" No Extent in Space 60" No Extent in Space 19 3/30/11 Physical World Anribute of Interest (Extent in Space) Infinite Extent in Space Physical World Anribute of Interest (Extent in Space) Infinite Extent in Space 72" 6" 66" 72" 6" 66" 6" 60" No Extent in Space 6" 60" No Extent in Space Physical World Anribute of Interest (Extent in Space) Infinite Extent in Space Physical World Anribute of Interest (Extent in Space) Infinite Extent in Space 72" 6" 66" 72" 6" 66" At least Interval 6" 60" 6" 60" No Extent in Space No Extent in Space 20 3/30/11 Physical World Anribute of Interest (Extent in Space) Infinite Extent in Space Physical World Anribute of Interest (Extent in Space) Infinite Extent in Space . 0" . No Extent in Space No Extent in Space Physical World Anribute of Interest (Extent in Space) Infinite Extent in Space Physical World Anribute of Interest (Extent in Space) Infinite Extent in Space 0" . 0" . RaKo No Extent in Space No Extent in Space 21 3/30/11 Physical World Anribute of Interest (Amount of Fear) Physical World Anribute of Interest (Amount of Fear) Most Possible Fear Physical World Anribute of Interest (Amount of Fear) Most Possible Fear No Fear No Fear 22 3/30/11 Physical World Anribute of Interest (Amount of Fear) Most Possible Fear Physical World Anribute of Interest (Amount of Fear) Most Possible Fear 9 4 5 4 1 No Fear 9 5 1 No Fear Physical World Anribute of Interest (Amount of Fear) Most Possible Fear Physical World Anribute of Interest (Amount of Fear) Most Possible Fear 9 4 5 4 1 No Fear 9 4 5 4 1 No Fear 23 3/30/11 Physical World Anribute of Interest (Amount of Fear) Most Possible Fear Physical World Anribute of Interest (Amount of Fear) Most Possible Fear 9 4 5 4 1 No Fear 9 4 5 4 1 No Fear At least Ordinal Physical World Anribute of Interest (Amount of Fear) Most Possible Fear Physical World Anribute of Interest (Amount of Fear) Most Possible Fear 9 4 5 4 1 No Fear 9 4 5 4 1 No Fear 24 3/30/11 Physical World Anribute of Interest (Amount of Fear) Most Possible Fear 9 4 5 4 1 No Fear Assumed Interval Scale Nominal Ordinal Interval Ra0o Labels for observa3ons Ordered Categories Equal Intervals Meaningful Zero point X X X X X X X X X X 25 3/30/11 Check Your Understanding A researcher measures "mood" as "the number of nights an individual sees his or her friends in a given month" On what scale is "mood" measured? Check Your Understanding A researcher measures "mood" as "the number of nights an individual sees his or her friends in a given month" On what scale is "mood" measured? A B C D Nominal Scale Ordinal Scale Interval Scale RaKo Scale A B C D Nominal Scale Ordinal Scale Interval Scale RaKo Scale Check Your Understanding Is the variable "mood" discrete or conKnuous? Check Your Understanding Is the variable "mood" discrete or conKnuous? A B Discrete ConKnuous A B Discrete ConKnuous 26 3/30/11 For Next Time Read Syllabus Chapter 1 and Appendix A Do Buy Clicker Buy Book 27 ...
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