Biostats

Question 1

Mode

Answer 1

the value that occurs most frequently

Question 2

Another term for normal distribution

Answer 2

Gaussian distribution
“bell-shaped curve”
68% values within 1 SD
95% within 2 SD

Question 3

Reject or accept null hypothesis?

Answer 3

Rejecting the null hypothesis means there IS a significant difference between the study groups
The researcher tries to disprove the null hypothesis

Question 4

WHat is the alpha value?

Answer 4

The max permissible error margin

Commonly 5% (0.05)

Question 5

Results are statistically significant when….

Answer 5

when the p-value is equal to or less than the alpha value
p < 0.05 = 95% probability the conclusion is correct
smaller p value = higher probability

Question 6

Data is significant when the CI does not contain zero (t/f)

Answer 6

TRUE

Question 7

Type I error =

Answer 7

False-positives
Null hypothesis is rejected, even though it was true
alpha value = chance of false positves

Question 8

Type II error =

Answer 8

False-negatives
Null hypothesis is accepted, when it should be rejected
Beta value = chance of false negatives
Study power = the probability that the test will reject the null hypothesis correctly (1 - Beta)

Question 9

Relative risk (RR)

Answer 9

risk in exposed group / risk in control group
RR = 1 = no difference
RR > 1 greater risk
RR < 1 less risk

Question 10

Discrete data

Answer 10

data that fits into limited distinct options
Nominal = categories (sex, ethnicity, etc)
Ordinal = categories that have an order (pain scale, HF classification)

Question 11

Continuous data

Answer 11

data is some type of measurement which has unlimited options
Ratio data: height, weight, BP (0 = none)
Interval data: temperature (0 equals something)

Question 12

T-test assess significance for what type of data?

Answer 12

continuous data
2 independent groups = unpaired t-test
3 or more samples = ANOVA

Question 13

What test is used to assess significant of nominal/ordinal data groups?

Answer 13

Chi square test

Question 14

test used to assess 2 groups with continuous data that is not normally distributed

Answer 14

Mann-WHitney (Wilcoxon Rank-Sum) test

Question 15

test used to assess 3+ groups with continuous data that is not normally distributed

Answer 15

Kruskal-wallis test (also used for categorical data with 3+ groups)
ANOVA for 3+ groups with continuous normally distributed data

Question 16

Independent variables can/cannot be changed by the reasearcher

Answer 16

CAN
drug dose, placebos, etc
dependent variables can change from the effects of the independent variables

Question 17

Types of correlation

Answer 17

Oridinal data: Spearman’s rank-order (rho)

continuous data: Pearson’s correlation coefficient (r; -1 to +1)

Question 18

Intention to treat vs. per protocol

Answer 18

intention to treat:
includes all pts in the analysis, even the pts that did not complete the study for various reason
more conservative analysis
Per protocol:
Only includes pts that completed the study

Question 19

Sensitivity of lab result

Answer 19

True positive

likelihood of test being + in a pt that has disease

Question 20

Specificity of lab result

Answer 20

True negative

likelihood of a test being - in pts that do not have the disease

Question 21

Rank study types from least reliable to most reliable

Answer 21

expert opinion -> case report/series -> Case-controlled -> cohort -> RCTs -> systematic review/meta-analysis

Question 22

Case-control study

Answer 22

compares pts with a disease (cases) vs without a disease (controls) and looks back in time (retrospectively)

Question 23

Cohort study

Answer 23

compares outcomes of pts exposed vs not exposed to a treatment
can be prospective of retrospective