What is the good will? What is DUTY? FOUR TYPES OF ACTION: I. Action contrary to duty (whether useful or not). II. Action in accordance with duty, performed from some indirect inclination. ADAM the actuarial shopkeepernot overcharging children for se
LAST TIME
CONFIDENCE
construct an interval around an
observed statistic, X
we never say that a 95% condence interval
contains with probability 0.95
Introduction to Statistics in
Psychology
PSY 201
either the interval contains or it does not
Professor Greg
Introduction to Statistics in
Psychology
PSY 201
Professor Greg Francis
Lecture 23
Hypothesis testing for correlations
HYPOTHESIS TESTING
HYPOTHESIS TESTING
four steps
we need to know the properties of the
sampling distribution
1. State the hypothesis.
2.
Introduction to Statistics in
Psychology
HYPOTHESIS TESTING
CONFIDENCE INTERVALS
four steps
sometimes have ve steps if want to
include CIs
PSY 201
Professor Greg Francis
Lecture 24
Correlations and proportions
1. State the hypothesis.
2. Set the criterion
Introduction to Statistics in
Psychology
HYPOTHESIS TESTING
TWO-SAMPLE CASE FOR
THE MEAN
PSY 201
H0 : = a
Professor Greg Francis
Ha : = a
useful when you want to compare
means of two groups
Lecture 25
Hypothesis testing for two sample case
Why do we let p
Introduction to Statistics in
Psychology
HOMOGENEITY OF
VARIANCE
HOMOGENEITY OF
VARIANCE
PSY 201
last time we noted that to carry out
hypothesis testing we need to calculate
standard error
turns out to be important only when
sample sizes are dierent, n1 =
Introduction to Statistics in
Psychology
PSY 201
Professor Greg Francis
Lecture 27
Hypothesis testing for dependent
sample means
Just relax.
DEPENDENT SAMPLES
CORRELATED DATA
two samples of data are dependent
when each score in one sample is
paired with a
Introduction to Statistics in
Psychology
PSY 201
TESTS
CORRELATIONS
To carry out a hypothesis test you
really just need to know a few things:
you have two independent populations
(not much need for tests with
dependent samples)
Professor Greg Francis
1) T
Introduction to Statistics in
Psychology
PSY 201
Professor Greg Francis
Lecture 29
Hypothesis testing for two sample
case
other statistics
What do people think about
death?
DEPENDENT SAMPLES
EXAMPLE
when the samples are not
independent, hypothesis testing
DESCRIPTION
RANGE
central tendency gives on indication of
where most, many, or average, scores
are
Highest score - lowest score + 1
Introduction to Statistics in
Psychology
PSY 201
Professor Greg Francis
Lecture 06
variability
standard scores
How to make
LAST TIME
POINT ESTIMATION
we know how to check if a sample
mean, X , is statistically signicantly
dierent from a hypothesized
population mean, .
single value that represents the best
estimate of a population value
Introduction to Statistics in
Psychology
DISTRIBUTION
GOAL
frequency of scores plotted against
score
describe (summarize) distributions
Introduction to Statistics in
Psychology
PSY 201
shape: unimodal, bimodal, skew,.
Professor Greg Francis
40
Lecture 07
Describing everyones height.
Frequency
n
Introduction to Statistics in
Psychology
PSY 201
Professor Greg Francis
Lecture 08
normal distribution
percentiles
NORMAL DISTRIBUTIONS
STANDARD NORMAL
when the distribution is a normal
distribution, we can describe the
distribution by just specifying
ass
Introduction to Statistics in
Psychology
PSY 201
Professor Greg Francis
Lecture 09
normal distribution
percentile ranks
A statistical approach to assigning
grades.
STANDARD NORMAL
PERCENTILE RANKS
assume you have a standard normal
distribution
(dont worry
CORRELATION
PSY 201
Lecture 10
plot value of one variable against the
value of the other variable
SAT scores, GPA
hours in therapy, self-esteem
correlation
grade on homeworks, grade on exams
Did I damage my daughters eyes?
number of risk factors, prob
LINEARITY
suppose you get r 0.
Does that mean there is no relation
between the data sets?
PSY 201
r is partly an index of how well a
straight line ts the data set
r = 0.903
Professor Greg Francis
many aspects of the data may aect
the value of r
Lecture 11
DISTRIBUTION
Introduction to Statistics in
Psychology
PSY 201
Professor Greg Francis
Lecture 15
Sampling distributions
Can you read my mind?
DICE ROLES
representation of all possible outcomes
area under the curve represents
relative frequency of events
co
Introduction to Statistics in
Psychology
PSY 201
Professor Greg Francis
INFERENTIAL STATISTICS
INFERENTIAL STATISTICS
when we get a set of data it is either
from all possible sources (population)
or a subset of sources (sample)
to estimate a parameter
( w
PSY 201
Professor Greg Francis
Lecture 17
Sampling distribution of the mean
Marvel at my predictive powers!
SAMPLING
DISTRIBUTION
suppose we have a population with a
mean and a standard deviation
the dierent X i sample means that are
calculated will be r
Introduction to Statistics in
Psychology
PSY 201
Professor Greg Francis
Lecture 18
Hypothesis testing of the mean
Why I dont use herbal medicines
SUPPOSE
HYPOTHESIS TESTING
we think the mean value of a
population of SAT scores is = 455
in hypothesis testi
SUPPOSE
HYPOTHESIS TESTING
the we think the mean value of a
population of SAT scores is = 455
with = 100
four steps
Introduction to Statistics in
Psychology
PSY 201
Professor Greg Francis
Lecture 19
Hypothesis testing of the mean
we take a sample of 144 f
Introduction to Statistics in
Psychology
PSY 201
Professor Greg Francis
Lecture 20
Hypothesis testing of the mean
Do nuclear plants make you sick?
UP TO NOW
UNKNOWN
if we know
of all the information we need, only
is hard to get
. From H0
X . From the
HYPOTHESIS TESTING
Introduction to Statistics in
Psychology
Professor Greg Francis
suppose I want to test whether a
population mean is dierent from a
value
Lecture 30
H0 : = 455
PSY 201
now further suppose that the
population mean really is dierent, say
i
Introduction to Statistics in
Psychology
HYPOTHESIS TESTING
Professor Greg Francis
suppose I want to test whether a
population mean is dierent from a
value
Lecture 31
H0 : = 455
PSY 201
Will your research project work?
State of nature
Decision made
H0 tru
WELCOME TO PSY 201
TA: Victor Servantes
Prof. Ehtibar Dzhafarov
D.S.Moore,G.P.McCabe,B.A.Craig
IntroductiontothePracticeofStatistics
7thedition,W.H.Freeman,2012
THIS IS YOUR TEXTBOOK
CourseWebSite(bookmarkit!)
http:/www.psych.purdue.edu/~ehtibar/f2016/psy
Lookingatdata:relationships
Scatterplots
IPSchapter2.1
responsevariable
explanatoryvariable,orpredictor
Student
Here, we have two quantitative
variables for 16 students.
1) How many beers they
drank, and
2) Their blood alcohol level
(BAC)
We are intereste