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Flashcards in 767 Midterm Notes (Imported) Deck (294)
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239

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

240

What are the characteristics of the normal curve?

1. Unimodality 2. Symmetry 3. Mathematical properties

241

What are properties of Z scores?

Standard scores with SD of 1, mean of 0, and range from -3 to 3.

242

What percentage of scores fall within +/- 1 SD of the mean in a normal distribution?

~68%

243

What percentage of scores fall within +/- 2 SDs of the mean in a normal distribution?

~96%

244

What percentage of scores fall within +/- 3 SDs of the mean in a normal distribution?

~99%

245

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%.)

246

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

247

What is the standard error of the mean?

a standard deviation of an infinite number of means, only chance error makes them fluctuate

248

What does it mean for a model to be linear?

No terms have powers greater than 1.

249

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?)

250

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”

251

What is within group variance?

variance of the means of the groups

252

What is standard variance of the mean?

standard error of the mean squared

253

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

254

How do F and T relate to one another?

- F= t^2
- t= (square root of) F

255

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).

256

What is the effect on mean of adding a constant to all variable scores?

Increases mean

257

What is the effect on variance of adding a constant to all variable scores?

No effect on variance

258

What is the effect on between-group variance of adding a constant to all variable scores?

Changes between group variance

259

What is the effect on within-group variance of adding a constant to all variable scores?

Does not affect within group variance

260

What is the relevance to the F test of not having independence of between group and within group variance?

F-test assumptions are violated

261

In Calculating of One Way Analysis of Variance, SSt = (equation)

SSb + SSW

262

In Calculating of One Way Analysis of Variance, SSt is (words)?

Sums of Squares Total

263

In Calculating of One Way Analysis of Variance, - SSb

Between Sums of Squares

264

In Calculating of One Way Analysis of Variance, - SSw

Within Sums of Squares

265

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)

266

What does significance of T or F tests not tell us?

Significance does not tell us magnitude of the effect/relation

267

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

268

How would one represent the factorial analysis of variance in the GLM?

y = ao + A + B + AB + e