12. Comparison of Several Means 1 Flashcards

1
Q

What do you use with 2 samples?

A

t-test

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2
Q

What is ANOVA?

A

analysis of variance

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3
Q

Why use an ANOVA instead of multiple t-tests?

A

when you run multiple t-tests, get an inflated familywise (type I error) rate

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4
Q

What does an ANOVA do?

A

tests whether 3+ means are the same or not

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5
Q

What type of test is an ANOVA?

A

omnibus test

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6
Q

What is an omnibus test?

A
  • tests for overall experimental effect

- doesn’t provide info regarding which groups were affected

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7
Q

f-stat equation

A

f-stat = model/error

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8
Q

What does the f-stat tell us?

A
  • only that the experimental manipulation had some effect

- doesn’t tell specifically what it was

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9
Q

ANOVA partitions variance into two categories

A
  • systematic

- unsystematic

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10
Q

SS_T

A
  • total sum of squares

- total amount of variation within a data set

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11
Q

SS_M

A
  • model sum of squares

- amount of systematic variation (explained by the model)

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12
Q

SS_R

A
  • residual sum of squares

- amount of unsystematic variation (not explained by the model)

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13
Q

MS_M

A
  • mean squares model

- SS_M ÷ df_M

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14
Q

MS_R

A
  • mean squares residual

- SS_R ÷ df_R

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15
Q

f-stat equation

A

MS_M ÷ MS_R

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16
Q

df_M

A

one less than the number of groups

k-1

17
Q

df_R

A

total degrees of freedom - df_M

N-K (total sample size - number of groups)

18
Q

What do you do once you calculate the f-stat?

A

compare to critical value with the same df in the appendix

19
Q

If the f-stat is more than the critical value:

A
  • difference between means due to more than chance

- significant difference

20
Q

If the f-stat is less than the critical value:

A
  • difference between means due to only chance

- not a significant value

21
Q

types of ANOVAs

A
  • one-way independent
  • factorial ANOVA
  • ANCOVA
22
Q

IVs for a one-way ANOVA

A

1 IV with between group differences

23
Q

IVs for a factorial ANOVA

A

2+ IVs

24
Q

What is an ANCOVA?

A

ANOVA with an addition of a covariate