Final Test Information

1
Final Test Information

• The final test is Monday, April 13 at 830 am
• GRH102 Last name begins with A - I
• GRH106 Last name begins with K - Z
• The exam is out of 40 15 multiple choice (worth
  15) 5 short answer (worth 25)
• It will cover material from the entire course,
  but the focus will be on ANOVA and correlation
• You will need to be able to identify when to do a
  z-test, t-test, ANOVA, and correlation
• Not all of the short-answer questions require
  calculations

2

• Statz Rappers

3
The Basics of Hypothesis Testing

1. State the null and research hypotheses in words
   and symbols
2. Determine the level of significance
3. Identify the critical value
4. Calculate the test statistic
5. Evaluate the test statistic in light of the
   critical value
6. Make a decision about the null hypothesis
7. State your conclusions in plain language

4
Statistical Tests Single sample mean

• Used to compare a single sample to a population
• Is the sample significantly different from the
  population?
• H0 µ X
• H1 µ ? X
• If you know the population standard deviation,
  then use a z-test
• If you do not know the population standard
  deviation, then use a t-test

5
Statistical Tests T-test for two related samples

• Used to compare two groups that are related in
  some way
• Are the two groups significantly different from
  each other?
• H0 µD 0
• H1 µD ? 0
• Could be a pre/post (i.e., before/after) design
• Could be two groups whose participants are
  related in some way (couples, twins, siblings
  etc).

6
Statistical Tests T-test for two independent
samples

• Used to compare two groups that are independent
  of each other
• Are the two groups significantly different from
  each other?
• Ho µ1 µ2
• H1 µ1 ? µ2

7
Statistical Tests Analysis of variance

• Used to compare three or more groups
• Are the groups significantly different from each
  other?
• Ho µ1 µ2 µ3
• H1 µ1 ? µ2 ? µ3
• If you reject your null hypothesis and conclude
  that there is a difference between the groups,
  you need to conduct post hoc (Tukey HSD) tests to
  determine which groups are different

8
ANOVA Summary Table

• Source df SS MS F
• Between K-1 MSBdfB SSB/dfB MSB/MSW
• Within N-K MSWdfW SSW/dfW
• Total N-1 SSB SSW

9
Statistical Tests Correlation

• Used to determine if there is a relationships
  between two variables
• Are the variables significantly correlated with
  each other?
• H0 r 0
• H0 r ? 0
• There are three ways to describe the relationship
  between the variables
• The direction and strength of the relationship
  (i.e., is r positive or negative, and how close
  is it to 1.0?)
• Is r significant (compare obtained value of r to
  critical value)?
• The amount of variance in one variable explained
  by the other (i.e., r2, the coefficient of
  determination)

10
Study Designs

• Experimental
• Looks for differences between groups of scores
• Uses terms like effect, difference, cause
• Use z-test, t-test or ANOVA to analyze data

• Correlational
• Looks for relationships between groups of scores
• Uses terms like relationship, correlation
• Use correlation to analyze data

11
Data Analysis Decision Tree for Experimental
Designs
How many groups?
2 groups Do a t-test
3 or moregroups Do an ANOVA
1 group (comparesample to population)
Are the scores related?
Is Fobt Fcrit?
Do you know the populationstandard deviation?
No T-test for independent samples
Yes T-test for relatedsamples
No Do not reject H0
Yes Reject H0 Conduct HSD post hoc test
No T-test for single samples
Yes Z-test forsinglesamples