PSYC 2022 - Statistical Methods II
SPSS Exercise #2
1. A researcher is interested in attitudes towards alternative medicines before and after a
talk on the advantages of these medicines. Specifically, the researcher would like to know if
attitudes towards
Interpreting p-values
Research Study Background
P A study is conducted to compare the means
of a treatment and control group
P Ho: 1 = 2; H1: 1 2
P for the study was set at .05
P A two independent samples t test is
conducted and the result is:
< t (18) =
PSYC 2022 - Statistical Methods II
ASSIGNMENT #1
Due Date: April 2, 2009 (4:00 pm). Submit the papers to Robs mailbox in the Psychology
Information Centre (101 BSB)
Dr. Black has developed a new method for treating test anxiety and would like to test it o
ONEWAY support BY educat
/STATISTICS DESCRIPTIVES
/MISSING ANALYSIS
/POSTHOC=TUKEY SCHEFFE ALPHA(0.05).
Oneway
Notes
Output Created
2009-05-11T09:06:37.093
Comments
Input
Data
Active Dataset
DataSet1
Filter
<none>
Weight
<none>
Split File
Missing Value Ha
Statistical Power
Statistical Power
Statistical power is the probability of
detecting a real effect
For example, if we were comparing males and
females on spatial ability, and (somehow) we knew
that there was a true difference between males and
females
Estimation
Estimation
The estimation process can produce either a point estimate or an interval estimate. A point estimate is a single value and has the advantage of being very precise. For example, based on sample data, you might estimate that the mean
GET
FILE='C:\My Documents\Robs Work\2022\Exercises\exer2_pairedsamps_t.sav'.
DATASET NAME DataSet1 WINDOW=FRONT.
T-TEST PAIRS=pretest WITH posttest (PAIRED)
/CRITERIA=CI(.9900)
/MISSING=ANALYSIS.
T-Test
Notes
Output Created
15-Apr-2009 16:02:32
Comments
I
PSYC 2022 - Statistical Methods II
Assignment #2
1. Dr. Smith is interested in determining if students at different academic levels differ in levels of
test anxiety. She randomly selects 10 first year, 10 second year, and 10 third year university
students
One-way Independent
Groups ANOVA
Effect Sizes, Post Hoc Tests, Assumption Violation
Effect Size in One-Way
Independent Groups ANOVAs
P The significance (or nonsignificance) of the F
test in a one-way independent groups
ANOVA tells us very little about how
Independent Samples t Test
Example
P Dr. Green wants to know if hockey players differ from soccer players in extraversion. He recruits 3 soccer players and 3 hockey players.
Step 1: State the hypotheses and alpha level
P Ho: 1 - 2 = 0 P H1: 1 - 2 0 P = .1
Wilcoxon Signed Ranks
Test
An Alternative to the Paired Samples t
The Wilcoxon Signed Ranks
Test
The Wilcoxon test can be viewed as an
alternative to the paired samples t test
The test uses data from one sample where
each individual has been observed in
Review Questions/Sample Short Answer Questions
1. What is an independent sample t test used for?
2. Why do we need an effect size to accompany the independent samples t test?
3. Why are directional tests more powerful than nondirectional tests?
4. When wo
PSYC 2022 - Statistical Methods II
Lab Exercise #1
Dr. Backs was interested in exploring whether differences in attitudes toward the Toronto Maple
Leafs (on a scale from 1-20) are a function of the location in which people live around the greater
Toronto
Two Independent Samples
t-test Under Nonnormality
Normality Assumption
P In computing Students t we need to assume
that the populations from which our groups
were sampled are normal in form
P Gravetter & Wallnau downplay the
importance of this assumption,
One-Way ANOVA
One-Way Analysis of Variance
One-Way ANOVA
The one-way analysis of variance is used
to test the claim that two or more
population means are equal
< The one-way ANOVA uses an F statistic and is
therefore often called the ANOVA F
This is an ex
Repeated-Measures
Analysis of Variance
Types of Within-Subject Designs
P True Within-Subjects Design
< Each subject is measured under each treatment
condition
< E.g., effects of amount of background noise on a
memory task (e.g., no background noise, 10 db
Dependent Samples t-test
Example
Example
P Dr. White wants to know if openness to
experience (OTE) scores improve after a
group of high school students goes on a
camping trip
P She records pre and post camping trip OTE
scores for a students
P The research
Review of Basic Statistics
Variables
A variable is a characteristic or condition
that can change or take on different values
Most research begins with a general
question about the relationship between
variables
Population
The entire group of individual
Factorial Designs
Introduction to Two-Way
Independent Groups Models
Introduction
P In the context of ANOVA, an independent
variable is called a factor, and research
studies with two factors are called factorial
designs or simply two-factor designs.
P When
Chapter 11: The t Test for
Two Related Samples
Repeated-Measures Designs
The related-samples hypothesis test allows
researchers to evaluate the mean difference
between two treatment conditions using the data
from a single sample.
In a repeated-measures
Chapter 8
A hypothesis test is a statistical method that uses sample data to evaluate a hypothesis
about a population.
Includes 4 steps to reach an hypothesis:
o First, we state a hypothesis about a population.
o Before we select a sample, we use the hypo