One-sample t-tests
The formula to solve for sample variance.
What is:
SS
n-1
The number of groups we are allowed to compare in an independent measures t-test.
2
The value of df if we have 24 people in the entire experiment
23
The type of statistic analysis/test we ran using the data on happiness that we gathered in class.
One sample t-test
What is the date of Exam #3?
November 9th
Name one problem with z-scores that make t-tests useful.
-
•The z-score requires more information than researchers typically have available
•Requires knowledge of the population standard deviation σ
•Researchers usually have only the sample data available
You have to calculate this when your n's are not the same size to ensure there is an unbiased statistic.
Pooled variance
If independent measures t-test is to related samples t-test
then between subjects design is to ____________?
repeated measures design OR within-subject design
What was the independent variable during our the activity we did for independent measures t-test?
Brand
When are my office hours?
Tuesday and thursday 2:45pm-4pm
Wednesday 9:30am-12pm
Name two things that describe the shape of a t distribution.
•Flatter than the normal distribution
•More spread out than the normal distribution
•More variability (“fatter tails”) in tdistribution
The 3 assumptions of an independent measures t-test.
-independent observations
-normality
-equal variances
Name two advantages of repeated measure designs.
•Requires fewer subjects
•Able to study changes over time
•Reduces or eliminates influence of individual differences
•Substantially less variability in scores
The type of test/statistical analysis that a coach would use if he was curious to see how quick his team can run a mile before and after lunch
related sample t-test
Name 4 things you have to bring to your exam.
-cheat sheet
-calculator
-t-distribution table / Appendix B
-writing instrument
The measure of effect size that looks at the percentage of variability accounted for by the treatment effect.
r2
If our confidence interval contains zero, what does this suggest?
non-significant results; fail to reject the null hypothesis
One solution to controlling time-related effects or order effects.
The name of the statistical software we use in this class that you had to download
SPSS
What is due tomorrow?
3 lab assignments, 2 homework assignments
The results of a hypothesis test are reported as follows: t(21) = 2.38, p < .05. What was the statistical decision and how big was the sample?
reject the null; n=22
The formula for a independent sample t-test
the difference between the observed sample means, minus the difference between the population means, divided by estimated standard error
Name two disadvantages of a repeated measures design.
Order effects; other factors may influence the results between measurements
All hypothesis tests should also be supplemented with this.
measure of effect size
What are the 4 steps of hypothesis testing?
1. state hypothesis
2. set criteria (alpha, directionality, critical value)
3. collect and analyze data
4. make a decision