exam 4

Question 1

what does anova test and what is the null

Answer 1

whether 3 or more group means are significantly different
H0= none of the means differ

Question 2

how do u calculate degrees of freedom in anova

Answer 2

df_ groups= k-1
df_ error= n-k
df_ total= n-1

Question 3

what is the formula for mean square in anova

Answer 3

ms=SS/df

Question 4

how do you find the f ratio in anova

Answer 4

MS_groups / MS error

Question 5

how do you calculate SS error

Answer 5

SStotal-SSgroups

Question 6

what is R^2 in ANOVA and how do you calculate it

Answer 6

SSgroups / SS total
tells you the proportion of variation explained by group differences

Question 7

when do you reject the null in ANOVA

Answer 7

Fcalculated> Fcritical

Question 8

what is k in anova

Answer 8

how many treatments

Question 9

what is a planned comparison

Answer 9

not testing all groups, just a specific one, before seeing the data

Question 10

what is an unplanned comparison in anova

Answer 10

comparison made after running anova, usually to see which group means differ

Question 11

when do you do unplanned comparisons

Answer 11

only after rejecting the anova null hypothesis

Question 12

what is the tukey kramer test used for

Answer 12

compare all pairs of means while controlling type one error rate across multiple comparisons

Question 13

what does persons r measure

Answer 13

the strength and direction of a linear relationship between 2 numerical variables

Question 14

what is the formula to test r- t test for correlation

Answer 14

t= r/SEr <- given SEr
df=n-2

Question 15

what is spearmans rank correlation used for

Answer 15

when data violates pearsons assumptions or when the relationship is not linear

Question 16

what is fischers z-transformation used for

Answer 16

calculate confidence interval for pearsons r

Question 17

what is the standard error for fischers z

Answer 17

1/sqrt n-3

Question 18

what does spearmans rank correlation measure

Answer 18

the strength and direction of a monotonic relationship

Question 19

when should you use spearmans instead of pearsons

Answer 19

when the data violate pearsons assumptions or the relationship is monotonic not linear

Question 20

effect of outliers on spearmans versus pearsons

Answer 20

spearmans- cares about rank, effect small
pearsons- could drop alot because that one point messes up the line

Question 21

what are the assumptions of pearsons correlation

Answer 21

1. linearity
2. normality
3. homoscedasticity
4. no major outliers
5. quantitive data

Question 22

how to calculate residuals

Answer 22

observed Y- predicted Y

Question 23

what is R^2

Answer 23

how much of the variation in Y is explained by X

Question 24

what is extrapolation

Answer 24

using the regression line to predict beyond he range of data -> not reliable

Question 25

what are the assumptions of anova

Answer 25

independence, normality, equal variance

Question 26

planned comparison equation?

Answer 26

t = (mean1 - mean2) / sqrt(MS_error * (1/n1 + 1/n2))

Question 27

tukey kramer test formula

Answer 27

q = |mean1 - mean2| / sqrt(MS_error * (1/n1 + 1/n2))

Question 28

fischers z transformation

Answer 28

z = 0.5 * ln((1 + r)/(1 - r)); SE_z = 1/sqrt(n - 3)

Question 29

what does slope b mean

Answer 29

Predicted change in Y for a 1-unit increase in X

Question 30

f test for regression

Answer 30

f=ms_regression/ Ms error

Question 31

how do you calculate r^2 in regression

Answer 31

ss regression/ ss total

Question 32

difference between confidence band and prediction interval

Answer 32

Confidence = mean Y at given X; Prediction = range for single Y value (wider)

Question 33

regression assumptions

Answer 33

Linearity (scatterplot), normality (hist/Q-Q), equal variance (residual plot), independence

Question 34

what is the main difference between planned and unplanned comparisons

Answer 34

unplanned- you test everyone against everyone planned-pre-picked battles

Question 35

how to look up q critical value for unplanned comparisons

Answer 35

k=. number of groups df error a level

Question 36

when looking up planned comparison in t table what do u use

Answer 36

df= n-k and a

Question 37

why do anova instead of multiple t tests

Answer 37

to avoid increasing the type 1 error rate

Question 38

fixed versus random effects in anova

Answer 38

fixed- factor levels are specifically chosen and we are only interested in comparing those levels random- levels are randomly selected from a larger population, trying to generalize

Question 39

what is the kruskal wallis test

Answer 39

nonparametric alternative way to anova, tests for differences between groups based on ranked data rather than means

Question 40

correlation measures

Answer 40

strength and direction of a relationship between 2 variables

Question 41

similarity between regression and correlation

Answer 41

same assumptions, both yield r^2

Question 42

what is attenuation

Answer 42

true correlation might be strong, but measured r is low because of inaccuracy in the data

Question 43

what is the method of least squares

Answer 43

the method used to find the best fitting regression line through a scatter plot aka residuals

Question 44

what does a bad residual plot look like

Answer 44

curve, funnel, clustering