Flashcards in 767 Midterm Notes (Imported) Deck (294)
What is the effect of increasing sample size on variance?
Decrease in variance as you come closer and closer to the "true" value in the population
What are the characteristics of the normal curve?
1. Unimodality 2. Symmetry 3. Mathematical properties
What are properties of Z scores?
Standard scores with SD of 1, mean of 0, and range from -3 to 3.
What percentage of scores fall within +/- 1 SD of the mean in a normal distribution?
What percentage of scores fall within +/- 2 SDs of the mean in a normal distribution?
What percentage of scores fall within +/- 3 SDs of the mean in a normal distribution?
How does one use the Normal Probability Curve of frequency data to interpret data?
Specify the probability that chance events will occur (e.g., - Chance of something occurring outside of range of Z2 is 4%, outside of Z3 is 1%.)
How does one calculate the Standard Error of Means?
SD (population SD approximated by sample SD) divided by the square root of cases in the sample
What is the standard error of the mean?
a standard deviation of an infinite number of means, only chance error makes them fluctuate
What does it mean for a model to be linear?
No terms have powers greater than 1.
What is the theoretical rationale of the t-ratio approach?
When we compare two means we want to ask do the means differ significantly? Or is the difference within the bounds of chance? (e.g., Does A differ from B beyond the difference expected by chance?)
What is the theoretical rationale of the Analysis of Variance Approach?
- A difference of two or more groups can be tested for significance.
- This method uses variance entirely and pits two variance against one another.
- One variance (independent, or experimental variable) pitted against a variance due to error or randomness
- Compare the “between group variance” with the “within group variance”
What is within group variance?
variance of the means of the groups
What is standard variance of the mean?
standard error of the mean squared
What is the F-Ratio?
1. Between Group Variance / Within Group Variance
2. - Your results are compared to F table. If higher than said number on the table, then results are significantly significant
How do F and T relate to one another?
- F= t^2
- t= (square root of) F
When does one use an F test over a t test?
- When comparing more than two groups F is used (t for two groups only).
What is the effect on mean of adding a constant to all variable scores?
What is the effect on variance of adding a constant to all variable scores?
No effect on variance
What is the effect on between-group variance of adding a constant to all variable scores?
Changes between group variance
What is the effect on within-group variance of adding a constant to all variable scores?
Does not affect within group variance
What is the relevance to the F test of not having independence of between group and within group variance?
F-test assumptions are violated
In Calculating of One Way Analysis of Variance, SSt = (equation)
SSb + SSW
In Calculating of One Way Analysis of Variance, SSt is (words)?
Sums of Squares Total
In Calculating of One Way Analysis of Variance, - SSb
Between Sums of Squares
In Calculating of One Way Analysis of Variance, - SSw
Within Sums of Squares
What does significance of T or F tests tell us?
That it is likely that an effect exists (is unlikely to be due to error)
What does significance of T or F tests not tell us?
Significance does not tell us magnitude of the effect/relation
What is factorial analysis of variance?
two or more independent variables vary independently or interact with each other to produce variation in a dependent variable