Mathematics / Statistics

Question 1

What is a Bland-Altman plot used for?

Answer 1

comparison of two different measurement techniques/assays

Question 2

How are standard error and standard deviation related?

Answer 2

SEM = SD / n^1/2

** SEM is always smaller than SD **

Question 3

What factors affect the confidence interval of a result?

Answer 3

sample size

mean

standard deviation

Question 4

What factors increase type 2 error (false negative rate)?

Answer 4

small sample size

high variability in the population

small alpha value

Question 5

How do you calculate the power of a study?

Answer 5

power = 1 - ß

** ß: type II error rate **

Question 6

What is the difference between interval data and categorical data?

Answer 6

interval data has a mean

Question 7

Which statistical tests are used for categorical data?

Answer 7

• Fischer exact test: for small samples
• Chi-squared test: for large samples
• Wilcoxon Rank Sum test or Mann-Whitney U test: for ordinal categorical data (i.e., VAS, ASA classification, APGARs, GCS)

Question 8

Which statistical tests are used for interval data?

Answer 8

• t-test: for 2 groups
• ANOVA: for more than 2 groups or 2 groups with multiple measurements
• Wilcoxon Rank Sum test or Mann-Whitney U test: data with a skewed distribution

Question 9

What kind of data are proportions?

Answer 9

categorical

** use Fischer’s exact test or Chi-squared test **

Question 10

What is the difference between linear regression and logistic regression?

Answer 10

• linear: involves a dependent continuous variable
• logistic: involves a dependent categorical variable

Question 11

What is the odds ratio?

Answer 11

odd ratio = risk among the exposed

risk among the unexposed