Introduction to Statistics for the Social Sciences SBS200 - Lecture Section 001, Fall 2017 Room 150 Harvill Building 10:00 - 10:50 Mondays, Wednesdays & Fridays. Welcome http://www.youtube.com/watch?v=oSQJP40PcGI

writing assignment forms notebook and clickers to each lecture Remember bring your writing assignment forms notebook and clickers to each lecture

Lab sessions No Labs next week Everyone will want to be enrolled in one of the lab sessions No Labs next week

“Serious Gamer” Score “Serious Gamer” Score “Serious Gamer” Score Time One positive correlation One negative correlation Comparing Two means “Serious Gamer” Score “Serious Gamer” Score “Serious Gamer” Score Time Studying Age Gender

Project 1 - Likert Scale - Correlations - Comparing two means (bar graph) Questions?

Sample versus population (census) How is a census different from a sample? Census measures each person in the specific population Sample measures a subset of the population and infers about the population – representative sample is good What’s better? Use of existing survey data U.S. Census Family size, fertility, occupation The General Social Survey Surveys sample of US citizens over 1,000 items Same questions asked each year

Population (census) versus sample Parameter versus statistic Parameter – Measurement or characteristic of the population Usually unknown (only estimated) Usually represented by Greek letters (µ) pronounced “mew” pronounced “mu” Statistic – Numerical value calculated from a sample Usually represented by Roman letters (x) pronounced “x bar”

Descriptive or inferential? To determine this we have to consider the methodologies used in collecting the data Descriptive or inferential? Descriptive statistics - organizing and summarizing data Inferential statistics - generalizing beyond actual observations making “inferences” based on data collected What is the average height of the basketball team? Measured all of the players and reported the average height Measured only a sample of the players and reported the average height for team In this class, percentage of students who support the death penalty? Measured all of the students in class and reported percentage who said “yes” Measured only a sample of the students in class and reported percentage who said “yes” Based on the data collected from the students in this class we can conclude that 60% of the students at this university support the death penalty Measured all of the students in class and reported percentage who said “yes”

Descriptive or inferential? Descriptive statistics - organizing and summarizing data Inferential statistics - generalizing beyond actual observations making “inferences” based on data collected Men are in general taller than women Measured all of the citizens of Arizona and reported heights Shoe size is not a good predictor of intelligence Measured all of the shoe sizes and IQ of students of 20 universities Blondes have more fun Asked 500 actresses to complete a happiness survey The average age of students at the U of A is 21 Asked all students in the fraternities and sororities their age

Time series versus cross-sectional comparisons: Trends over time versus a snapshot comparison Time series design: Each observation represents a measurement at some point in time. Repeated measurements allow us to see trends. Cross-sectional design: Each observation represents a measurement at some point in time. Comparing across groups allows us to see differences. Traffic accidents Please note: Any one piece of data can often (not always) be used in either a time series comparison or a cross-sectional comparison. It depends how you set up your question. Does Tucson or Albuquerque have more traffic accidents (they have similar population sizes)? Does Tucson have more traffic accidents as the year ends and winter approaches?

Time series versus cross-sectional comparisons: Trends over time versus a snapshot comparison Time series design: Each observation represents a measurement at some point in time. Repeated measurements allow us to see trends. Cross-sectional design: Each observation represents a measurement at some point in time. Comparing across groups allows us to see differences. Unemployment rate Is there an increase in workers calling in sick as the summer months approach? Do more young workers call in sick than older workers? Grade point average (GPA) Does GPA tend to go up or down as students move from freshman to sophomores to juniors to seniors? Does GPA tend to go up or down when you compare Mr. Chen’s class with Mr. Frank’s Freshman English classes?

So far, Measurement: observable actions Theoretical constructs: concepts (like “humor” or “satisfaction”) Operational definitions Validity and reliability Independent and dependent variable Random assignment and Random sampling Within-participant and between-participant design Single blind (placebo) and double blind procedures

So far, Continuous vs Discrete variables Quantitative vs qualitative variables Levels of measurement: Nominal, Ordinal, Interval and Ratio Population (census) versus sample Parameter versus statistic Descriptive or inferential Time series versus cross-sectional comparisons

What is the independent variable? Amount of sleep Does amount of sleep (4 vs 8 hours) affect class attendance? Selected 350 students who happened to be walking along the mall from 38,000 undergraduates at U of Washington and randomly assigned students into two groups. What is the independent variable? Amount of sleep How many levels are there of the IV? 2 levels (4 hours vs 8 hours) What is the dependent variable? Group 1 gets 4 hours sleep Class attendance What is population and sample? Note: Parameter would be what we are guessing for the whole school based on these 350 students Population: whole school Sample: group of 350 students What is statistic ? Group 2 gets 8 hours sleep Average class attendance for 350 students Quasi versus true experiment (random assignment)? True Random sample? No, not all students equally likely to be on mall

What is the independent variable? Gender of teacher Does gender of the teacher affect test scores for the students in California? Selected 150 students from Santa Monica and then just asked them to report the gender of their teacher. What is the independent variable? Gender of teacher How many levels are there of the IV? 2 levels (male vs female teacher) What is the dependent variable? Group 1 gets a female teacher Test Scores What is population and sample? Population: California Sample: group of 150 students from Santa Monica What is statistic ? Group 2 gets a male teacher Average test score for 150 students Quasi versus true experiment (random assignment)? No, no random assignment, just used current teacher Random sample? No – Random sample would require that everyone in California be equally likely to be chosen.

Let’s try one A study explored whether eating carrots really improves vision. Half of the subjects ate a package of carrots everyday for 3 months while the other group did not. Then, they tested the vision for all of the subjects. The independent variable in this study was a. the performance of the subjects on the vision exam b. the subjects who ate the carrots c. whether or not the subjects ate the carrots d. whether or not the subjects had their vision tested

Let’s try one A study explored whether eating carrots really improves vision. Half of the subjects ate a package of carrots everyday for 3 months while the other group did not. Then, they tested the vision for all of the subjects. The dependent variable in this study was a. the performance of the subjects on the vision exam b. the subjects who ate the carrots c. whether or not the subjects ate the carrots d. whether or not the subjects had their vision tested

Let’s try one A study explored whether eating carrots really improves vision. Half of the subjects ate a package of carrots everyday for 3 months while the other group did not. Then, they tested the vision for all of the subjects. This experiment was a a. within participant experiment b. between participant experiment c. mixed participant experiment d. non-participant experiment

Let’s try one When Martiza was preparing her experiment, she knew it was important that the participants not know which condition they were in, to avoid bias from the subjects. This is called a _____ study. She also was careful that the experimenters who were interacting with the participants did not know which condition those participants were in. This is called a ____ study. a. between participant; within participant b. within participant; between participant c. double blind design; single blind d. single blind; double blind design

Let’s try one A measurement that has high validity is one that a. measures what it intends to measure b. will give you similar results with each replication c. will compare the performance of the same subjects in each experimental condition d. will compare the performance of different subjects

Let’s try one A study explored whether conservatives or liberals had more bumper stickers on their cars. The researchers ask 100 activists to complete a conservative/liberal values test, then used those results to categorize them as liberal or conservative. Then they identified the 30 most conservative activists and the 30 most liberal activists and measured how many bumper stickers each activist had on their car. The independent variable in this study was a. the performance of the activists b. the number of bumper stickers found on their car c. political status of participant (liberal versus conservative) as determined by their performance on the liberal/conservative test d. whether or not the subjects had bumper stickers on their car

Let’s try one A study explored whether conservatives or liberals had more bumper stickers on their cars. The researchers asked 100 activists to complete a conservative/liberal values test, then used those results to categorize them as liberal or conservative. Then they identified the 30 most conservative activists and the 30 most liberal activists and measured how many bumper stickers each activist had on their car. The dependent variable in this study was a. the performance of the activists b. the number of bumper stickers found on their car c. political status of participant (liberal versus conservative) as determined by their performance on the liberal/conservative test d. whether or not the subjects had bumper stickers on their car

Let’s try one A study explored whether conservatives or liberals had more bumper stickers on their cars. The researchers 100 activists to complete a conservative/liberal values test, then used those results to categorize them as liberal or conservative. Then they identified the 30 most conservative activists and the 30 most liberal activists and measured how many bumper stickers each activist had on their car. This study was a a. within participant experiment b. between participant experiment c. mixed participant experiment d. non-participant experiment

Let’s try one A study explored whether conservatives or liberals had more bumper stickers on their cars. They had 100 activists complete liberal/conservative test. Then, they split the 100 activists into 2 groups (conservatives and liberals). They then measured how many bumper stickers each activist had on their car. This study used a a. true experimental design b. quasi-experiment design c. correlational design d. mixed design

Writing Assignment – Pop Quiz Ari conducted a watermelon seed spitting experiment. She wanted to know if people can spit farther if they get a running start. She tested 100 people. She randomly assigned them into one of two groups. One group stood still on the starting line and spit their watermelon seeds as far as they could. The second group was allowed to run up to the starting line before they spit their watermelon seeds. She measured how far each person spit their watermelon seeds. Please answer the following questions 1. What is the independent variable? 2. The independent variable: Is it continuous or discrete? 3. The independent variable: Is it nominal, ordinal, interval or ratio? 4. What is the dependent variable? 5. The dependent variable: Is it continuous or discrete? 6. The dependent variable: Is it nominal, ordinal, interval or ratio? 7. Is this a quasi or true experiment? 8. Is this a within or between participant design 9. Is this a single blind, double blind or not at all blind experiment? 10. Be sure to put your name and CID on this page

Writing Assignment – Pop Quiz Ari conducted a watermelon seed spitting experiment. She wanted to know if people can spit farther if they get a running start. She tested 100 people. She randomly assigned them into one of two groups. One group stood still on the starting line and spit their watermelon seeds as far as they could. The second group was allowed to run up to the starting line before they spit their watermelon seeds. She measured how far each person spit their watermelon seeds. Running versus standing still Please answer the following questions 1. What is the independent variable? 2. The independent variable: Is it continuous or discrete? 3. The independent variable: Is it nominal, ordinal, interval or ratio? 4. What is the dependent variable? 5. The dependent variable: Is it continuous or discrete? 6. The dependent variable: Is it nominal, ordinal, interval or ratio? 7. Is this a quasi or true experiment? 8. Is this a within or between participant design 9. Is this a single blind, double blind or not at all blind experiment? 10. Be sure to put your name and CID on this page Discrete Distance that the seed was spit Nominal Continuous True Experiment Ratio Between Not at all

Thank you! See you next time!!