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t-tests between + within Flashcards

(13 cards)

1
Q

If obtained t score is larger than t-table, probability of getting that large by chance is…

A

less than .05 P<.05
reject the null hypothesis

the independent variable is influencing something

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2
Q

Between-subjects t-test
ASSUMPTIONS

A
  1. dependent on interval or ratio scale
  2. both samples norm distr
  3. populations equal variance - homogeneity, levenes test
  4. Independence of observations
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3
Q

Between subjects t-test STEPS

A
  1. estimate popn SD (each group)
  2. pooled s2pool (n -1)
  3. Standard error of mean diffs. (n is whole number)
  4. mean differences
  5. t-score using what you calculated
  6. t-table, obtained larger than table reject null
  7. cohens d uses s2 pool
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4
Q

one-tailed

A

one
- double the alpha level .1 on table
- know before ‘a priori’ whether correlation is positive or negative
- null r = 0
- positive r > 0
- negative r < 0

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5
Q

two-tailed

A

two
- 0.05 on table
- cant predict/doesnt specify whether correlation + or -
- null = no correlation btwn variables
- alternative = is correlation

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6
Q

Outcomes - null or alternative hypothesis

A

H0 null = the groups show no performance difference
H1 = the groups show performance difference

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7
Q

bessels correction N-1

A

only for estimating, ie population standard deviation

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8
Q

T-Distribution is

A

the distribution obtained from an estimated population SD

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9
Q

t-score is

samples over or under estimate standard error?

A

how many standard error units our sample mean is away from the mean

Samples OVERestimate standard error
t is platy, increase sample =z-norm

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10
Q

effect size

Cohens D values

A

estimates proportion of variability in scores on dependent variable explainable by variation in the level of the indepdendent variable
- is result meaningful?

small .2, med .5 large .8

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11
Q

repeated measures (Within) is

A

experience both levels of condition (IV)

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12
Q

Repeated measures assumptions

A
  • dependent variable on interval/ratio
  • sample diff scores norm distrib.
  • scores are related across conditions
    –> same individual
    –> less variability of individual differences
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13
Q

repeated-measures steps

A
  1. estimate variance of popn
  2. estimate standard error
  3. obtained t-value
  4. t-table (if obtained is larger, reject null)
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