PSYC 2117
Spring 2013
T-Test Independent Means
T-Test Independent Means
Independent T-Test
Single Sample T- Sample vs. Population
Tamiu Stats Students vs. Tamiu Students
Dependent Means T- One sample, two tests
Before and After effect
Beginning of Semeste
PSYC 2117
Spring 2013
ANOVA
ANOVA
Within Groups Estimate of the Population Variance= S2Within
Variance within a set of scores
Group 1: 20, 21, 21, 22,5, 40
Not affected whether Ho is true or false
Determined by error, chance factors
ANOVA
Between groups e
PSYC 2117
Spring 2013
Hypothesis Testing
Hypothesis Testing
State the research question as a hypothesis and null hypothesis
Hyp- Students who take a class with an instructor who uses an active approach will have
better grades
Null (ho) - There is no diffe
PSYC 2117
Spring 2013
Hypothesis
What is a Hypothesis?
Expected outcome
Based on previous literature (studies)
Are not always going to be correct
Prediction
Can be changed or corrected
Why do we need to have a hypothesis?
"It is hypothesized that children
PSYC 2117
Spring 2013
Analysis of Variance
Analysis of Variance
Testing Groups
When testing two groups the measure used is a T-Test
Determining the effects of the treatment vs. control
Key importance is two groups
Testing Groups
Ex: The effects of positiv
PSYC 2117
Spring 2013
Effect Size
Effect Size
An effect can be statistically significant without having much practical significance
Reject Null with P<.001
Effect Size
Difference
Change
Overlap
Smaller Effect size more overlap
Effect Size
Raw Score Effect
PSYC 2117
Spring 2013
Statistical Power
Statistical Power
What is statistical power?
Ability to reach significance
Probability to reach significance if Ho is false or research hyp (h1) is true
Low Power = Small chance of reaching significance
High Power=
PSYC 2117
Spring 2013
Hypothesis Tests with Means of Samples
Single scores:
Taking sample
Mean
Z scores
Means of samples: more than one individual
Many samples
Not single scores
Populations has known mean and SD
Distribution of Means: a distribution of th
PSYC 2117
Spring 2013
T-Test
T-Test
One Sample T-Test
Hypothesis testing:
Used for comparing different groups- One sample
Unknown information requires the use of t-test
Same group- Repeated measures
Difference between T and Z test
Distribution
Degrees of
PSYC 2117
Spring 2013
Distribution on T-Tests
Distribution
Sample size affects t-distribution
Larger sample the closer the curve is to being normal.
Large sample- higher df
Higher df-use normal cutoff scores
Distribution
Larger N, smaller SD
Smaller N, wi