SLIDE 1
Quality Control Quality Control
Part 1/2
Fair?
Heads Heads Heads Heads Heads Heads 6/6 .031 .5
5
Quality Control Quality Control Part 1/2 Fair? Heads 6/6 Heads - - PowerPoint PPT Presentation
Quality Control Quality Control Part 1/2 Fair? Heads 6/6 Heads - - PowerPoint PPT Presentation
Quality Control Quality Control Part 1/2 Fair? Heads 6/6 Heads Heads 5 .5 Heads Heads .031 Heads Sample Size Heads 6/6 Heads Heads 5 .5 Heads Heads .031 Heads you flipped 6 times; could have flipped more or less Null
SLIDE 2
SLIDE 3
Heads Heads Heads Heads Heads Heads 6/6 .031
Sample Size
you flipped 6 times; could have flipped more or less
.5
5
Heads Heads Heads Heads Heads Heads 6/6 .031
Null Hypothesis
what might we refute? the hypothesis that the coin is fair
.5
5
Heads Heads Heads Heads Heads Heads 6/6 .031
Statistical Significance
the probability of getting a result at least as extreme as this (is .031 enough to be convincing?)
.5
5 (p-value)
SLIDE 4
Null Hypothesis Significance Testing
how unlikely would it be for you to find the data you found if there were no effect of interest Democrats like blue, Republicans like red…
NH: Ds and Rs like red the same Preference
9 18 27 36 45 Election Day Democrats Republicans
Preference for Red
p < .01
(conventionally: reject the null hypothesis if p < .05)
SLIDE 5
Null Hypothesis Statistical Significance Sample Size
Heads Heads Heads Heads Heads Heads 6/6 .031
Sample Size
.5
5
Sample Size
how many is enough? 100? 10? 10000? no right answer; but, all else equal, more data will allow you to be more confident in your findings the “same” sample size can mean very different things
SLIDE 6
Sample Size
no right answer; but, all else equal, more data will allow you to be more confident in your findings the “same” sample size can mean very different things how many is enough? 100? 10? 10000?
Experimental Design
Between Subjects Within Subjects
Is a good night’s sleep better than an all-nighter for exam performance? 100 people
50 sleep 8 hrs before Intro Psych exams #1 and #2 50 pull all-nighters before Intro Psych exams #1 and #2
100 people
50 sleep 8 hrs before Intro Psych exam #1, and pull all- nighter before exam #2 50 pull all-nighter before Intro Psych exam #1, and sleep 8 hrs before exam #2
Experimental Design
Between Subjects Within Subjects
Sleep No Sleep 92 70 88 85 65 S1 S2 S3 S4 S5 Avg 80 85 64 91 68 82 S6 S7 S8 S9 S10 Avg 78 Sleep No Sleep 92 70 88 85 65 S1 S2 S3 S4 S5 Avg 80 91 68 85 82 64 S1 S2 S3 S4 S5 Avg 78 Is a good night’s sleep better than an all-nighter for exam performance?
SLIDE 7
Quality Control
Up next: Part 2/2
Quality Control
Part 2/2
SLIDE 8
Average yearly temperature The lowest temperature each year
SLIDE 9
The highest temperature each year The highest temperature each year, by season The highest summer temperature each year
SLIDE 10
The highest temperature each summer, since 1918
If you do enough tests, you can “discover” almost anything!
and if you only tell everyone about the tests that “worked”, you mislead your readers!
Divorce rate in MaineDivor ce r ate in M aine
correlates with
Divorce rate in M aine 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 3.96 per 1,000 4.29 per 1,000 4.62 per 1,000 4.95 per 1,000 tylervigen.com????
SLIDE 11
What correlates very highly with the divorce rate in Maine?
# of jobs lost in Maine
A C lbs. of margarine consumed nationally B Church attendance
Divorce rate in MaineDivor ce r ate in M aine
correlates with
Divorce rate in M aine 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 3.96 per 1,000 4.29 per 1,000 4.62 per 1,000 4.95 per 1,000 tylervigen.com????
Margarine consumed Divorce rate in MaineDivor ce r ate in M aine
correlates with
Per capita consumption of mar gar ine
M argarine consumed Divorce rate in M aine 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2lbs 4lbs 6lbs 8lbs 3.96 per 1,000 4.29 per 1,000 4.62 per 1,000 4.95 per 1,000 tylervigen.comhttp://www.tylervigen.com/spurious-correlations
SLIDE 12 Margarine consumed Divorce rate in Maine
Divor ce r ate in M aine
correlates with
Per capita consumption of mar gar ine
M argarine consumed Divorce rate in M aine 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2lbs 4lbs 6lbs 8lbs 3.96 per 1,000 4.29 per 1,000 4.62 per 1,000 4.95 per 1,000 tylervigen.comcorrelate thousands of random things with thousands of other random things something will emerge eventually…
- nly show us that!
SLIDE 13
If you do enough tests, you can “discover” almost anything!
Does listening to “When I’m 64” make you younger?
Yes! Subjects who listened to “When I’m 64” gave their age as 20 years old; subjects who listened to “Kalimba” gave their age as 22 years old But wait…
SLIDE 14
Does listening to “When I’m 64” make you younger?
Subjects listened to either “When I’m Sixty-Four” by The Beatles
- r “Kalimba” or “Hot Potato” by the Wiggles. Then, they
indicated their birth date, how old they felt, how much they would enjoy eating at a diner, the square root of 100, their agreement with “computers are complicated machines,” their father’s age, their mother’s age, whether they would take advantage of an early-bird special, their political orientation, which of four Canadian quarterbacks they believed won an award, how often they refer to the past as “the good old days,” and their gender.
SLIDE 15
“women showed psi effects to highly arousing stimuli but men did not” women, men arousing, not arousing positive, negative 4, 6, 8, or 10 exposures “women showed psi effects to highly arousing stimuli but men did not” women, men arousing, not arousing positive, negative 4, 6, 8, or 10 exposures
{
3 3 3 5+
x x x
at least 135 possible tests!
SLIDE 16
“women showed psi effects to highly arousing stimuli but men did not” women, men arousing, not arousing positive, negative 4, 6, 8, or 10 exposures
{
3 3 3 5+
x x x
- ne was bound to
yield a rare result
“Researcher degrees of freedom”
undisclosed flexibility in experimental design and analysis that can lead to spurious “effects” not always apparent; be on the lookout! Take “research methods in experimental psychology” with Prof. Jeff Bowen!