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Stats and data analysis (y2s1) > Week 3 Lecture 3 - Independent 1-way ANOVA > Flashcards

Week 3 Lecture 3 - Independent 1-way ANOVA Flashcards

1
Q

What does ANOVA mean?

A

analysis of variance

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2
Q

When is an ANOVA test used?

A

when we have 1 IV with more than 2 levels

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3
Q

What does an ANOVA test estimate?

A

whether the pop. means under the different levels of the IV are different
based on sample means

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4
Q

How is ANOVA an extension of the t-test?

A

F = t^2

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5
Q

What is the familywise error rate?

A

the probability that at least 1 of a “family” of comparisons, run on the same data, will result in a type 1 error

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6
Q

What does the familywise error rate provide?

A

a corrected sig. level, expressing the probability of making a type 1 error

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7
Q

How is the familywise error rate calculated?

A

a’ = 1 - (1 - a)^c

a = level of confidence we’re working to for each comparison (normally = .05)
c = number of comparisons

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8
Q

what type of test is the ANOVA test?

A

omnibus test

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9
Q

What is the f ratio?

A

variance between IV levels / variance within IV levels

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10
Q

If F values are close to 0 what does this mean?

A

small variance BIVL relative to WIVL

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11
Q

If F values are further from 0 what does this mean?

A

large variance BIVL relative to WIVL

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12
Q

What contributes to variance BIVL?

A
  • manipulation of IV
  • individual difference
  • experimental error (random and constant error)
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13
Q

What contributes to variance WIVL?

A
  • individual differences
  • experimental error (random error)
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14
Q

How do you calculate the grand mean?

A

Sum of IV level means, divided by the number of IV levels

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15
Q

How is variance partitioned?

A

1.) calc means for each IV level
2.) calc the grand mean –> sum of IV level means divided by no. of IV levels
3.) Calc WIVL variance –> sum of squared differences between individual values and the corresponding IV level means
4.) calc BIVL variance –> sum of squared differences between each IV level mean and the grand mean

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16
Q

What are the assumptions for an independent 1-way ANOVA test?

A
  • normality
  • homogeneity of variance
  • equivalent sample size
  • independence of observations
17
Q

If the assumptions for an independent 1-way ANOVA test are seriously violated, what should you do?

A

use non-parametric equivalent –> Kruskai Wallis Test

18
Q

How is an F stat reported?

A

F(dfM, dfR) = f-value, p = p-value

19
Q

If homogeneity is violated in the I1-W ANOVA, what should you do?

A

use Welch’s F test

20
Q

What is Welch’s F test?

A

DF adjusted to be more conservative
gives slightly higher p-value

21
Q

How do you report a Welch f value?

A

F(dfM, dfR) = f-value, p = p-value (Welch)

22
Q

What is the Model Sum of Squares (SSm)?

A

sum of squared differences between IV level means and grand mean (BIVL variance)

23
Q

What is the Residual Sum of squares (SSr)?

A

sum of squared differences between individual values and corresponding IV level mean (WIVL variance)

24
Q

How do you calculate SSt?

A

SSm + SSr

25
Q

How do you calculate Mean Squared m (MSm)?

A

SSm / DFm

26
Q

How do you calculate Mean Squared r (MSr)?

A

SSr / DFr

27
Q

How do you calculate an F stat?

A

MSm / MSr

28
Q

How many DOF do you need in I1-W ANOVA?

A

2
1 for BIVL and 1 for WIVL

29
Q

How do you cal DOF for BIVL in I1-W ANOVA?

A

k-1 (k = no. of IV levels)

30
Q

How do you cal DOF for WIVL in I1-W ANOVA?

A

N - k

31
Q

What is a post-hoc test?

A
  • used to assess which IV level mean pairs differ
  • only used when f-value is sig.
  • ran as a t-test but includes correction for multiple comparisons
  • there are a choice of corrections, they vary in their risk of Type 1 and Type 2 error
32
Q

What is the error risks and classifications for the Tukey Honestly Significant Difference (HSD)?

A

Type 1 error risk = low
Type 2 error risk = high
Classification = “reasonably conservative”

33
Q

What are the 2 effect sizes that are calculated for ANOVA?

A

partial ETA^2
Cohens d

34
Q

What is partial ETA^2?

A

how much variance in the DV is explained by the manipulation of the IV overall

35
Q

What are the effect sizes for partial ETA^2?

A

small > .01
medium > .06
large > .14

36
Q

How do you calculate partial ETA^2?

A

SSm / (SSm + SSr)

37
Q

When do you calculate Cohen’s D?

A

for each pair in post-hoc tests

Stats and data analysis (y2s1) (9 decks)

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