Paired Ttest and Independent Ttest Anova

Question 1

What are 2 related groups

Answer 1

• Intervention group & a matched control group
• Pretest/posttest measures on the same person
• Twin studies

Question 2

Describe a grouping variable

Answer 2

• Defines the 2 related groups being compared
• Is the independent variable
• Ex: pretest time & posttest time (same person) or person & matched control

Question 3

Characteristics of interest variable

Answer 3

• Interval or ratio
• Is the dependent variable measured at 2 points in time or b/w a case & control
• Ex: BP premedication & postmedication, weight (case & control)

Question 4

Describe a paired t Test

Answer 4

• Compares the means of 2 related groups
• Parametric test (assumes a normal distribution)
• Reports the mean of each group
• Reports the standard deviation of each group

Question 5

Define a-level (alpha level)

Answer 5

• Statistical significance will defined as p≤0.05
• If number is below the Alpha level then you reject the null hypothesis
• If number is above the Alpha level then accept the null hypothesis

Question 6

We establish Alpha level and the computer establishes the p-value (True/False)

Answer 6

• True

Question 7

Steps in performing a t Test

Answer 7

• State the null & alternative hypothesis
• Define the a-level & find the critical value
• Ensure the data meet the assumptions
• Compute the t Test statistic
• Determine statistical significance & state a conclusion

Question 8

Describe an independent t Test

Answer 8

• Compares the means of 2 unrelated groups
• Parametric test (assumes a normal distribution)
• Reports the mean of each group
• Reports the standard deviation of each group

Question 9

Describe a one-way ANOVA test

Answer 9

• Compares the means of ≥3 independent groups defined by one factor (grouping variable)
• Parametric test (assumes a normal distribution)
• Assumes homogeneity of variance b/w the groups
• Reports the mean & standard deviation of each group

Question 10

How does ANOVA work

Answer 10

• ANOVA models compare within & b/w group variance to determine if the means of the groups are different from one another
• Within group variance: the variance of the variable within each group
• B/w group variance: the variance (spread) of he group means from each other
• Ratio of the within group variance to the b/w group variance follows an “f” distribution & is referred to as an “f-ratio”

Question 11

Describe the ANOVA and post hoc tests

Answer 11

• An ANOVA model can only tell us if one or more of the means are statistically significantly different from the others
• Post-hoc tests are necessary to tell which means are different
• These tests are conducted only if the overall ANOVA model is statistically significant