Biostats 1

Question 1

Stating that there is not an effect or difference when one exists

Answer 1

Type II error (beta)

Question 2

Stating that s an effect or difference when none exists

Answer 2

Type I error (alfa)

Question 3

Values affected by prevalence of a disease

Answer 3

PPV ➡️ increases when ⬆️ prevalence

NPV ➡️ increases when ⬇️ prevalence

Question 4

Extreme and unusual observed value in a data test. Mode is not affected.

Answer 4

Outlier

Question 5

Formula for number needed to harm

Answer 5

NNH= 1/AR

*AR: attributable risk

Question 6

Define Attributable risk

Answer 6

Difference in risk between exposed and unexposed groups.
Event rate of treated - event rate control
AR= a/(a+b) - c/(c+d)
AR%= (RR-1)/RR x100

Question 7

Relative risk characteristics

Answer 7

Used in cohort studies.
Risk of developing a disease in the exposed group divided by risk in the unexposed group.
RR=1 ➡️ no association
RR greater than 1 ➡️ exposure associated with ⬆️ disease occurrence
RR lesser than 1 ➡️exposure associated with ⬇️ disease occurrence

Question 8

Relative risk formula

Answer 8

a/(a+b) / c/(c+d)

Question 9

Odds ratio characteristics

Answer 9

Used in case-control studies.
Represents the odds of exposure among cases (a/c) vs odds of exposure among controls (b/d)
OR=1 ➡️ exposure equal among disease/no disease
OR greater than 1 ➡️ exposure ⬆️ among disease/no disease
OR lesser than 1 ➡️exposure ⬇️ among disease/no disease

Question 10

Formula for number needed to treat

Answer 10

NNT= 1/ARR

*ARR: Absolute risk reduction

Question 11

Define absolute risk reduction

Answer 11

The difference in risk attributable to the intervention as compared to a control
Event rate control (placebo) - event rate of treated
ARR= c/(c+d) - a/(a+b)

Question 12

Probability of rejecting the null hypothesis, represents a study’s ability to detect a difference when one exists.

Answer 12

Statistical power (1-beta)

Question 13

Statistical technique used to describe the effect that one or more independent variables (quantitative, qualitative) can have on one quantitative dependent variable

Answer 13

Regression analysis

Question 14

Factor related to both exposure and outcome distorts effect of exposure on outcome. Can result in the false association of an exposure with a disease

Answer 14

Confounding bias

Question 15

This type of study compares the effect of a series of 2 or more treatments on a participant. The order of tx is randomized and a washout period occurs between each one

Answer 15

Crossover study

Question 16

This statistical test checks differences between 2 or more percentages or proportions of categorical (qualitative) outcomes

Answer 16

Chi-square test