Bivariate Analysis: Independent T-Test and ANOVA Flashcards
What is an Independent T-Test?
Measures a Continuous variable and compared across two Discrete independent groups
What is a Two Group Comparison research design entail?
1 Group receives an experimental treatment
1 Group receives a placebo or usual care
What does the independent variable measure in an Independent T-Test?
Discrete, nominal
What does the dependent variable measure in an Independent T-Test?
Continuous, ratio
What factors influence the size of t in an Independent T-Test?
- Difference between the means (X1-X2)
- Variability (sp2)
- Sample Size (n)
How does the Difference between the Means change t?
As the difference between the mean increases, the value of t increases
How does the Variability change t?
As variability value increases, the value of t decreases
How does the Sample Size change t?
As the sample increases, the value of t increases
In an Independent T-Test the hypothesis includes what?
The comparison of means between independent groups
What is an ANOVA test?
Measures a continuous variable, compared across 3 or more Discrete Independent groups
ANOVA is a 2 Step Process, what are the steps?
- Test for differences among the group means
- If yes, then a follow up test to identify which specific groups are different from one another
What are the assumptions that must be made to complete an ANOVA test?
- Random Samples
- Independent Samples
- Independent observations within groups
- Normally distributed data
- Equal variances
What is the first step of the ANOVA?
F Test for H0: no difference among group means
The F Test for H0 looks at what?
F-Statistic
P-Value
If p-value is less than significance level, reject H0
What is the second step of the ANOVA?
Post Hoc* Test
The Post Hoc* Test is what?
Modified version of T-Test, pairwise comparisons
Post Hoc = After the event
What is a Familywise Type 1 Error Rate?
The probability of making at least one type 1 error when multiple tests are conducted on the same variable in independent samples increases with each additional test
What tests corrects for the Familywise Type 1 Error Rate?
Post Hoc
What does the HA of an ANOVA test suggest?
At least ONE population mean does not equal another population mean
If you reject the null hypothesis, you can conclude that at least one population mean is different but it cannot conclude that ALL of the population means are different? You must use what test to analyze this?
Post Hoc, used to determine which specific means are different
What are the 2 sources of Variance in an ANOVA test?
- Between: variance between the various groups
- Within: variance within each group
What is the Total Variance?
Variance between groups + Variance within groups
How do you partition variances?
Alleviate negative numbers by squaring
Sum of squares
What is SSB?
Sum of the square differences BETWEEN the group means and the grand mean
