Welcome to Psych 315, Spring 2014 ‘Understanding Statistics in Psychology’

1. Welcome to Psych 315, Spring 2014 ‘Understanding Statistics in Psychology’ Instructor: Geoffrey Boynton TAs: Frank Schwebel (Sections AA and AB) Anton Mates (Sections AC and AD) Undergraduate TA: Anna Chong Course website:http://courses.washington.edu/psy315/

2. By the end of this quarter you should know how to: -compute a statistic (means, variances, etc.) -represent data in graphical form (bar graphs, scatter plots…)-make a statistical inference (generalize from sample a population) -interpret a results section in an APA journal paper -make conclusions from statistics presented to you in everyday life

3. What is/are ‘statistics’? Statistics: The science of classifying, organizing and analyzing data Statistic: A descriptive index of a sample. (e.g. average) What are statistics good for? Probably most important: Interpreting data sets in an objective way. Example: consider a graph showing Obama’s approval ratings over a six month period

4. One of these is real, the rest are randomly generated. Which is real? 52 52 50 50 48 48 Approval (%) Approval (%) 46 46 44 44 42 42 Apr May Jun Jul Aug Sep Apr May Jun Jul Aug Sep 52 52 50 50 48 48 Approval (%) Approval (%) 46 46 44 44 42 42 Apr May Jun Jul Aug Sep Apr May Jun Jul Aug Sep 52 52 50 50 48 48 Approval (%) Approval (%) 46 46 44 44 42 42 Apr May Jun Jul Aug Sep Apr May Jun Jul Aug Sep 52 52 50 50 48 48 Approval (%) Approval (%) 46 46 44 44 42 42 Apr May Jun Jul Aug Sep Apr May Jun Jul Aug Sep

5. Recommended (but not required) reading:

6. Statistics in the news: March 19, 2014 Lied-to children more likely to cheat, lie The study tested 186 children ages 3 to 7 in a temptation-resistance paradigm. Approximately half of the children were lied to by an experimenter, who said there was "a huge bowl of candy in the next room" but quickly confessed this was just a ruse to get the child to come play a game. The others were simply invited to play, with no mention of candy. About 60 percent of the school-aged children who had not been lied to by the experimenter peeked at the tricky temptation toy -- and about 60 percent of the peekers lied about it later. Among those that had been lied to, those figures rose to nearly 80 percent peeking and nearly 90 percent of the peekers lying.

7. Statistics in the news: March 25, 2014 Shorter sleepers are over-eaters, study in children shows The study found that 16 month-old children who slept for less than 10 hours each day consumed on average 105kcal more per day than children who slept for more than 13 hours. This is an increase of around 10% from 982kcal to 1087kcal.

8. Statistics in the news: March 30, 2014 Tooth loss linked to depression, anxiety At the conclusion of this national study, the researchers found that depression and anxiety are associated with tooth loss. There were 76,292 eligible participants; and 13.4% of participants reported anxiety, 16.7% reported depression, and 5.7% reported total tooth loss. In Chi-square analysis by tooth loss: depression, anxiety, and a combined category of depression or anxiety were significantly different in tooth loss (p <0.0001).

9. Statistics in the news: September 21, 2012 Study says genetically modified corn causes tumors, but other scientists skeptical about research ...mice who were fed either a diet of Monsanto's genetically modified maize sprayed with Roundup - the company's brand of weed killer - or drank water with levels of Roundup similar to what is found in U.S. tap water were much more likely to die and at an earlier age, in addition to other health problems. Critics also taken issue with the study's methodology. Specifically the researchers' choice of rats are known for their propensity to develop mammary tumors if their diet is not controlled. Also, the control group of just 20 mice is rather small and makes it hard to draw conclusions from comparisons.

10. Statistics in the news: September 24, 2012 ‘Garden trampolining 'dangerous and should be discouraged', say doctors Dr Michele LaBotz, who co-authored a new AAP policy statement on their dangers, said: “Pediatricians need to actively discourage recreational trampoline use.” Three-quarters of injuries occur when more than one person is on a trampoline, according to studies she examined. Common injuries in all age groups include sprains, strains and contusions. Children under five are at particular risk, with 48 per cent of injuries in this age group resulted in fractures or dislocations.

11. Statistics in the news: September 22, 2011 Depression tied to higher risk for stroke Researchers analyzed 28 previous studies, which involved a total of almost 318,000 people and 8,478 stroke cases. The investigators found that depression was associated with a 45 percent increased risk for stroke and a 55 percent raised risk for fatal stroke.

12. Statistics in the news: September 21, 2012 Can it! Soda studies cite stronger link to obesity For DRINK (Double-Blind Randomized Intervention in Kids), they gave 641 children aged about 5 to 12 and with a healthy BMI of just under 17 one 8-ounce (250 milliliter) noncarbonated drink per day, sweetened artificially or with sugar. The sugar-free drinks were specially formulated to look and taste like sugary ones so the kids would not know which they had. About a quarter of the kids stopped drinking the beverages. Among those who stuck it out for 18 months, the sugar-free kids gained less body fat, 2.2 pounds (1 kilogram) less weight, and 0.36 units less BMI than the sugary-drink kids, the researchers report in the NEJM.

13. Statistics in the news: September 26, 2011 Coffee cuts depression risk in women Participants were followed from 1996 to 2006 to see whether they were diagnosed with depression. None of the participants had depression at the study's start. Women were considered depressed if they had been given a diagnosis of clinical depression by their physician and they started taking antidepressants. Over the 10-year period, 2,607 new cases of depression were reported. Women who drank four or more cups of coffee per day were 20 percent less likely to develop depression than those who drank one or fewer cups of coffee per week.

14. Statistics in the news: March 10, 2010: Stanford Survey Finds iPhone Addicting Stanford University has released the results of a survey of 200 students who own iPhones and found 10 percent characterized themselves as fully addicted to the device, or five on a scale of one to five, while 34 percent rated themselves as fours and only six percent said they were ones. The survey found 75 percent of respondents admitted to falling asleep with their iPhone in bed, while 69 percent were more likely to forget their wallet than their iPhone. Forty-one percent characterized the possible loss of their iPhone as “a tragedy.”

15. Statistics in the news: September 27, 2011 Childlessness May Increase Men's Heart Disease Risk As a group, childless men and men with one child were 13 percent more likely to die from cardiovascular disease than men with two or more children. The results held even after the researchers took into account factors that could affect risk of dying from heart disease, including body-mass index (BMI), activity level, tobacco and alcohol use, income and education.

16. Statistics in the news: March 11, 2010: Variable Blood Pressure a New Stroke Risk Factor? People with the greatest variation in systolic blood pressure (the higher of the 120/80 readings) over seven visits to their doctor were six times more likely to have a major stroke. People with the highest blood pressure readings were 15 times more likely to have a stroke.

17. Chapter 1: Introduction Some basic definitions population: the complete set of observations about which an investigator wishes to draw conclusions parameter: a descriptive index of a population sample: subset of a population statistic: a descriptive index of a sample (a number that summarizes a sample) Analogy: A parameter is to a population as a statistic is to a sample Random sample: a sample pulled from the population obtained in way that ensures that each sample of a given size has an equal chance of being selected from the population.

18. Chapter 1: Introduction Two kinds of statistics: Descriptive and Inferential • Descriptive Statistics (Chapters 1-11) • Summarize observations with numbers • The mean is the most common descriptive statistic Examples: The Mariners’ 2013 team batting average was .237 Average high temperature for a given date (56 deg for March 31st in Seattle) The median cloud cover is 95% for the month of march

19. Two kinds of statistics: Descriptive and Inferential Inferential Statistics (Chapters 12-22) - Used to draw a conclusion about a population based a sample. Example: Suppose you want to know the average IQ of all Washington State citizens. How would you do this?

20. Scales of Measurement: Nominal, Ordinal, Interval, Ratio Nominal Scale: mutually exclusive categories. Can’t be put in order Example: rocks can be categorized as igneous, sedimentary and metamorphic Ordinal Scale: like nominal, but the categories can be ranked in order. Example: Winter Olympics Ice Dancing Scores Interval Scale: like ordinal, but distance between measures has the same meaning across the entire range of values. Ratios are not meaningful Examples: Temperature in Fahrenheit, Years A.D. Ratio Scale: like interval, but the value of zero has meaning. Ratios are meaningful. Examples: Temperature in Kelvin, height, weight, age, measures of time

21. Name that scale: Nominal, Ordinal, Interval, Ratio Favorite color Speed (mph) Year A.D. Rating on a scale from 0 to 10 Response time Average high temperature (Fahrenheit) Favorite number Handedness Mohs scale of mineral hardness (the hardness of a minerals as measured by its ability to scratch a softer one)