chi-squared and t-tests (w6)

Question 1

what test to use when proportions with more than 2 levels

Answer 1

chi-squared goodness of fit test

Question 2

what test to use when comparing proportions across 2 or more groups

Answer 2

chi squared test of association

Question 3

what test to use when comparing a measure with a fixed value

Answer 3

one sample t test

Question 4

what test to use when comparing a measure across 2 groups ( independent and paired )

Answer 4

independent: two samples t test
paired: paired t test

Question 5

what test to use when comparing measure across more than two groups

Answer 5

ANOVA

Question 6

what is chi squared a test of

Answer 6

test of difference among categorical (nominal and ordinal) variables

Question 7

what are two types pf chi squared test

Answer 7

goodness of fit
test of association (or test of independence)

Question 8

what is chi squared goodness of fit test for

Answer 8

how proportions in data fit to fixed (expected) proportions

Question 9

what is chi squared test of association for

Answer 9

how proportions of two data sets are associated

Question 10

what is Benford’s law, aka

Answer 10

first digit law
the frequency of first digits of naturally occurring numerical data follow a particular proportion (eg prices, populations, lengths)

Question 11

what does the chi squared test for Benford’s law test

Answer 11

whether the frequencies of first-digits of the data follow the known proportion

Question 12

what is null for testing Benford’s law, what does it mean if its rejected

Answer 12

Benford’s law is preserved (i.e. numbers are naturally occurring)
data set is likely fabricated

Question 13

how to report chi squared goodness of fit test

Answer 13

the X2 value for df followed by p-value
eg: X2 (5) = 12.2, p=0.032

Question 14

in chi squared goodness of fit test, what does bigger X2 mean

Answer 14

bigger difference

Question 15

what can descriptive statistics for chi squared test of association be summarised as

Answer 15

contingency table

Question 16

how to report chi squared test of association results

Answer 16

X2 value with df and N (number of samples) followed by p-value
eg: X2 (2, N=27) = 1.43, p = 0.490

Question 17

what’s a paired sample

Answer 17

means data points are paired across 2 groups
eg is variables are mom L or R handed and daughter is L or R handed, mom-daughter data need to be paired

Question 18

when can McNemar’s test be used

Answer 18

only for 2 dichotomous variables (ie 2-by-2 contingency table)

Question 19

what is t test for, what variables

Answer 19

difference in group of measures (interval or ratio variables), compare means of populations (3 or more means use a different test)

Question 20

what is null hypothesis for t test

Answer 20

that means are equal

Question 21

what are three types of t test

Answer 21

one sample
independent (unpaired) samples
paired samples

Question 22

what you can decide for each t test

Answer 22

whether to do a one-tailed or two-tailed test

Question 23

what test for nominal/ordinal variables the one sample t test corresponds to

Answer 23

binomial or chi squared goodness of fit

Question 24

what test for nominal/ordinal variables the independent (unpaired) samples t test corresponds to

Answer 24

chi squared test of association

Question 25

what test for nominal/ordinal variables the paired samples t test corresponds to

Answer 25

McNemar's test

Question 26

whats the one sample t test for

Answer 26

compares mean of one sample group against a fixed value

Question 27

what is independent samples t test for, why is data called independent

Answer 27

compare the observed difference between the means of two independent samples or categories data is from different groups

Question 28

what is paired samples t test for

Answer 28

compare the main difference of one group measure on two occasions

Question 29

what does normality assumption for t test mean, what is this called

Answer 29

sampling distribution of the mean is normal central limit theorem

Question 30

what are statistical tests based on normality assumption called

Answer 30

parametric tests

Question 31

how to check normality assumption, what indicates violation of normality

Answer 31

test of normality (shapiro-wilk test) low p value (p<0.05)

Question 32

what's an assumption for independent samples t test

Answer 32

equality of variance: variance of 2 populations are equal

Question 33

how to test equality of variance, what is p value in this context

Answer 33

Levene's test of equal variance, significance of difference in variances are reported as p value

Question 34

how to know if variance is/isn't equal, what to do if variances aren't equal

Answer 34

p < 0.05 : variance not equal p > 0.05 : variance are equal use Welch's test

Question 35

how to write result for one sample t test

Answer 35

eg: UoB students reported higher levels of stress (M = 62, SD = 4) than found in the population of the same age group, t(36) = 2.4, p = .034

Question 36

how to write result for independent samples t test

Answer 36

There was no significant effect of gender on the exam score, t(138) = 3.7, p =.097, despite women (M = 65, SD = 8) attaining higher scores than men (M = 61, SD = 6.8)

Question 37

how to write results for paired samples t test

Answer 37

The results from the pre-test (M = 12.1, SD =1.4) and post-test (M = 14.1, SD = 1.7) memory task indicate that energy drink have significantly improve the memory, t(19) = 3.1, p = .006

Question 38

what does t value depend on

Answer 38

df = sample size - no. groups

Question 39

what does greater t value mean

Answer 39

greater difference, usually reported with M and SD

Question 40

when to use one sample t test

Answer 40

one group, normality

Question 41

when to use Wilcoxon signed ranks test/one-sample median

Answer 41

one group, no normality

Question 42

when to use independent samples t test

Answer 42

two groups, unpaired, normality, equal variance

Question 43

when to use Welch's test

Answer 43

two groups, unpaired, normality, no equal variance

Question 44

when to use Mann-Whitney U test

Answer 44

two groups, unpaired, no normality

Question 45

when to use paired samples t test

Answer 45

two groups, paired, normality

Question 46

when to use Wilcoxon signed ranks test

Answer 46

two groups, paired, no normality