Psych 202 - Test 3

Question 1

degrees of freedom

Answer 1

the number of scores that are free to vary when estimating a population parameter

Question 2

why do we subtract by 0 in the mean

Answer 2

we assume that the population and sample mean are the same, so there will be no difference (0) when subtracted from each other

Question 3

estimated variance

Answer 3

• we do not know the variance so we have to estimate it
• if the null is true and we pull the sample from the population, the means and standard deviations should be the same
• biased estimate with more likelihood of error
• sample variance will always be small than population variance

Question 4

divide by N - 1

Answer 4

to correct for the biased nature of the estimated variance

Question 5

t-distribution

Answer 5

t < 30 = platykurtic

t > 30 = in between platykurtic and normal

Question 6

t-table

Answer 6

always go to lower number when looking at values

• rather be more conservative
• i.e. looking for 45 with choice between 43 and 50 –> go with 43 because we know we have 43 with our “group”

Question 7

t-test

Answer 7

• used when population variance/standard error is unknown (our denominator in the final equation)

Question 8

ANOVA

Answer 8

analyzes how much variance is due to randomness vs. how much is due to treatment/population differences

Question 9

difference score

Answer 9

change (A) - base (B)

> always subtracting the base from the specific

Question 10

between group variance

Answer 10

measures difference between the separate groups

- more difference expected than in within variance

Question 11

within group variance

Answer 11

measures difference within the separate groups

- ideally 0

Question 12

planned contrast

Answer 12

• within (group variance and df) stays the same
• between changes (group variance and df)
• recalculate the between variance and df with contrast scores instead of original data