Statistical tests

Question 1

One sample T-test

Answer 1

• used to compare mean of a single sample with a known population mean to check if the sample is derived from the described populations
• needs two values- the observed mean and the population mean
• variable must be normally distributed
• sample size must be adequate enough to prevent extreme skewness

Question 2

Two sample t test

Answer 2

• Student’s t
• used to compare means of two samples
• needs independent variable and dependent variable
• unpaired t test compared independent smaples
• paired t test compare the same group e.g pre and post test
• t-test assumes equal variance among the two groups of given data (use Levene’s test to check)

Question 3

ANOVA

Answer 3

• used to compare means of multiple groups
• based on variance comparison
• one way ANOVA is used for one independent variable compared across more than 2 groups
• 2 way ANOVE has 2 independent variables
• repeated measures ANOVE is used when the same measure is used on multiple occasions ie. paired observations
• ANOVA is calculated using the ratio of variation between groups to the variation within groups- F statistics

Question 4

Disadvantage of ANOVA

Answer 4

• can only tell us if a significant difference exists among groups but doesnt say where the difference comes from
• assumes normal distribution and equal variance

Question 5

1 mean

Answer 5

One sample t test

Question 6

Two means- unpaired

Answer 6

Two sample t test

Question 7

Two means paired

Answer 7

Paired T test

Question 8

More than two unpaired means

Answer 8

One way ANOVA

Question 9

More than two paired means

Answer 9

MANOVA

Question 10

One Median

Answer 10

Sign test

Question 11

Two Medians unpaired

Answer 11

Mann-Whitney U test

Question 12

Two medians paired

Answer 12

Wilcoxon rank sum test

Question 13

More than two groups of unpaired medians

Answer 13

Kruskal Wallis test

Question 14

More than two groups of paired medians

Answer 14

Friedman test

Question 15

Two proportions- unpaired

Answer 15

Chi Square test

Question 16

Two proportions paired

Answer 16

McNemar test

Question 17

More than two proportions unpaired

Answer 17

Log linear or logistic regression

Question 18

Parametric tests

Answer 18

• used if at least one variable is quantitative and normally distributed
• t-tests or ANOVAs

Question 19

Non-parametric tests

Answer 19

• used when a) both dependent and independent variables are qualitative (nominal or ordinal) or b) when the variables are quantitative but not normally distributed
• ranks are compared
• sign test, wilcoxon rank sum, mann-whitney U, Kruskal wallis

Question 20

Sign test

Answer 20

-simple non-parametric test that compares the median of a sample to the median of the population

Question 21

Wilcoxon rank sum test

Answer 21

-used to compare the two paired observations in non-parametric fashion

Question 22

Mann-Whitney U

Answer 22

-used for independent observations in two groups

Question 23

Kruskal-Wallis

Answer 23

-used for 3 or more groups parametrically

Question 24

Transformation of data

Answer 24

-log transformation is used to convert data into a form more acceptable for parametric analysis

Question 25

Log transformation

Answer 25

• most common transformation of data

- in right skew this yields a normal distribution (lognormal curve)

Question 26

Square root transformation

Answer 26

• has normalising and linearising properties
• stabilises variance
• normalises Poisson distributions

Question 27

Reciprocal transformation

Answer 27

-used in survival rates

Question 28

Logit transformation

Answer 28

• used in the distribuution of proportions

- linearises a sigmoid curve

Question 29

Chi square x2 test

Answer 29

• commonly used non-parametric test
• used for comparing frequency counts or proportions
• contingency table is made like a 2x2 table
• observed frequencies vs expected outcomes (if null hypothesis was true)
• ration between observed to expected frequencies in the cells of the table is the chi square

Question 30

Fisher’s exact test

Answer 30

-used in place of chi-square if the expected cell frequencies in more than 20% of cells falls less than 5

Question 31

Yates correction

Answer 31

-used if the total sample was less than 100 or any cell was less than 10 in chi squared

Question 32

McNemar test

Answer 32

-X2 test for paired data

Question 33

Mantel-Haenszel test

Answer 33

-form of chi square test wherein the influence of two dichotomous categorical variables on one dependent variable is tested

Question 34

Log-linear analysis

Answer 34

• used in chi-square test where log-values of cell frequencies are employed
• this is when more than 2 groups or variable are studied