DatAna

Question 1

What is the null hypothesis?

Answer 1

→no statistically significant difference in the

relevant endpoint exists (or will be observed) between the groups

Question 2

What is the alternate hypothesis?

Answer 2

→statistically significant difference

does exist between the groups

Question 3

What should the hypothesis detail?

Answer 3

→key endpoint, dependent variable, or parameter is being measured
and compared between groups

Question 4

What is the p-value?

Answer 4

→estimates the probability of the
difference observed between the groups occurring due to random variation in
the data if there was not any genuine difference between the groups

Question 5

What is p<a></a>

Answer 5

→the difference is statistically significant → H0 rejected

Question 6

What is p>a?

Answer 6

→the difference is not statistically significant → H0 retained

Question 7

What is a smaller alpha value more likely to result in?

Answer 7

→result in a false positive as
very strong evidence of a statistically significant difference is required to
reject the null hypothesis

Question 8

What is a greater alpha value more likely to result in?

Answer 8

→a false positive as
only weak evidence of a statistically significant difference is required to
reject the null hypothesis

Question 9

What is the unpaired t-test?

Answer 9

→analyse the statistical significance of differences
between the means of two groups, where the data is parametric (normally
distributed) and samples are independent (unpaired)

Question 10

What variables can impact the p-value by t-test?

Answer 10

→the magnitude of the difference between the mean values of the two groups,

→the standard deviation,

→ the number of samples in each group

Question 11

What is a two-tailed test?

Answer 11

→assesses whether there is a statistically significant difference
between one group and another, regardless of whether it is an increase or a
decrease

→X being
different to Y

Question 12

What is a one-tailed test?

Answer 12

→only assesses whether there is a statistically significant
increase/decrease between one group and another

→X being
greater than/less than Y

Question 13

When are non-parametric methods used?

Answer 13

→evidence that the variable/data

in question is not normally distributed

Question 14

What is the Mann-Whitney U test?

Answer 14

→non-parametric equivalent of the unpaired t-test used to assess whether
differences between two groups of independent samples are statistically
significant

Question 15

How is Mann-Whitney U test carried out?

Answer 15

→assigning ranks to the data values
observed in the study

→estimating the probability of the ranks being
distributed between the two groups in the manner observed due to random
variation

Question 16

What is used to measure the central tendency for non-parametric data?

Answer 16

→median rather than the mean which is used in parametric

Question 17

How can we determine whether data is parametric or non-parametric without a test?

Answer 17

→the data (when expressed as a histogram) can be visually inspected to
subjectively judge whether the shape is approximately normal

→whether there is substantial kurtosis (flattening/peaking) or skewing
(asymmetry)

Question 18

How can we determine whether data is parametric or non-parametric with a test?

Answer 18

→Shapiro-Wilks test

evaluates the null hypothesis that the data is not normally distributed

Question 19

How do we interpret the Shapiro-Wilks test?

Answer 19

→If
the p-value calculated is less than the chosen alpha (threshold value,
e.g. 0.05) there is sufficient evidence to indicate that the data is non-
parametric, otherwise the data is assumed to be parametric due to there
being insufficient evidence to reject the null hypothesis

Question 20

Define paired data

Answer 20

→Samples are dependent if each group contains the same samples; each
experimental condition involves the same set of participants

→eg. the same group of participants have their blood pressure
measured before and after taking a drug

Question 21

Define unpaired data

Answer 21

→Samples are independent if each group contains different samples; each
experimental condition involves a different set of participants, animals, cells,

→E.g. one group of participants is treated with a drug, a different group of
participants is treated with placebo

Question 22

What type of test for paired and non-parametric data?

Answer 22

→Wilcoxon Signed-Rank

Question 23

What type of test for unpaired and non-parametric data?

Answer 23

→Mann-Whitney U test

Question 24

What can result if multiple t-test are conducted for multiple comparisons?

Answer 24

→increased likelihood of type-1

errors (false positives)

Question 25

What test is used for multiple comparisons?

Answer 25

→ANOVA followed by post test

Question 26

What is a one-way ANOVA?

Answer 26

→test the null hypothesis that there are no | statistically significant differences between any of the groups

Question 27

When is a post test carried out?

Answer 27

→If the result of the ANOVA is statistically significant →o evaluate the statistical significance of specific combinations of pairwise comparisons

Question 28

What are the types of post-tests?

Answer 28

→Bonferroni →Dunnet →Turkey

Question 29

What is Bonferroni?

Answer 29

→used when the researcher wishes to select specific pairwise comparisons that do not a have particular pattern to them

Question 30

What is Dunnet's?

Answer 30

→used when there are multiple groups to be compared to | a control group

Question 31

What is Turkey's?

Answer 31

→when a study requires pairwise comparison of every | possible combination of groups

Question 32

What does the ANOVA test assume?

Answer 32

→independent samples and parametric | data

Question 33

What are the alternatives to ANOVA?

Answer 33

→ The Kruskal-Wallis test (or ‘Kruskal-Wallis ANOVA’) is used when data is non-parametric. ``` →A repeated measures ANOVA (rANOVA) is used to compare groups with dependent samples (paired data) and where data is parametric. ``` →The Friedman test is a non-parametric alternative to the rANOVA.

Question 34

When is a two-way ANOVA used?

Answer 34

→analyse studies investigating whether there is | interaction between multiple factors

Question 35

What does a two-way ANOVA examine?

Answer 35

→There are no statistically significant differences in the dependent variable between the groups based on factor 1 (e.g. there is no significant difference in the mean blood pressure of participants between drug-treated and control treated groups) →There are no statistically significant differences in the dependent variable between the groups based on factor 2 (e.g. there is no significant difference in the mean blood pressure of male participants and female participants) →There is no statistically significant interaction between factor 1 and factor 2 in relation to the dependent variable (e.g. there is no significant interaction between the effect of treatment on blood pressure and participant’s sex).

Question 36

What is an alternative to two-way ANOVA?

Answer 36

→Aligned Rank Transformation | →non-parametric data, rank based alternatives can be used

Question 37

What test is used for categorical data?

Answer 37

→Pearson’s chi-squared test

Question 38

What is the Pearson's chi-squared test?

Answer 38

→there is no statistically significant difference | between the frequency distribution of different outcomes for different groups

Question 39

What post tests can be used to compare specific pairs of groups or outcomes?

Answer 39

→Bonferroni correction

Question 40

What test is used for unpaired categorical data?

Answer 40

→McNemar’stest

Question 41

What is Fisher's test appropriate for?

Answer 41

→analysing 2x2 contingency tables (i.e. two groups of samples and two possible options for the categorical variable) and when sample size is low (n < 10)