ClinEpi

Question 1

Risk difference

Answer 1

risk (incidence) of a disease in one group minus risk (incidence) of a disease in another group

Question 2

Attributable risk

Answer 2

Ie - Iu

• Ie = incidence in exposed
• Iu = incidence in unexposed

Attributable risk is the risk difference when referring to factors that increase the risk of disease.

Question 3

Attributable risk percent (AR%)

Answer 3

(Ie-Iu)/Ie

• Ie = incident in exposed
• Iu = incidence in unexposed

Attributable risk percent is the percent of risk in the exposed group that is attributable due to the exposure.

Question 4

Absolute Risk Reduction (ARR)

Answer 4

ARR = Ic - Irx

• Ic = incidence in control group
• Irx = incidence in treatment group

Absolute risk reduction is the risk difference in context of treatment effects.

Question 5

Relative Risk (RR)

Answer 5

RR = Ie/Iu (or Irx/Ic)

• Ie = incidence of exposure
• Iu = incidence without exposure
• Irx = incidence in treated group
• Ic = incidence in control group

Question 6

Relative Risk Reduction (RRR)

Answer 6

RRR = Ic - Irx/Ic

RRR = ARR/Ic

• Ic = incidence in control group
• Irx = incidence in treated group

Percentage of baseline risk that is removed as a result of general therapy.

Question 7

Number needed to treat (NNT)

Answer 7

NNT = 1/(Ic - Irx)

NNT = 1/ARR

How many patients need to be treated to prevent one outcome event.

Question 8

Standard Deviation

Answer 8

The measure of the degree of variability in individual measurements in a study.

Question 9

Standard error

Answer 9

The measure of dispersion of sample means around the population mea (the amount of variability in the overall mean).

Question 10

Null hypothesis (Ho)

Answer 10

States that there is no difference in outcomes between comparison populations.

Question 11

Type I error

Answer 11

false +

(think that there is a difference but there is not)

Question 12

Type II error

Answer 12

false negative

(think that there is no difference but there is one)

Question 13

P value

Answer 13

probabiliyt of finding an outcome as extreme or more extreme than the one we found assuming the null hypothesis is true

“how likely it is that this is all chance”

Question 14

Confidence interval

Answer 14

calculated ange of values surrounding the point estimate that are consistent with the true effect (95% confidence interval for which there is a 95% chance that it contains a true value of difference). It is statistically significant if null value is not crossed.

Question 15

Statistical power

Answer 15

Study’s ability to detect a difference assuming that a real difference exists.

Question 16

Clinical importance

Answer 16

The salience of finding for clinical practice and is related to the magnitude of the finding, taking into account the seriousness of the outcome and the prevalence of the condition.

Question 17

Test Statistic

Answer 17

effect size X sample size /SD

great test statistic lower p value

Question 18

Is a statistically significant result always clinically significant?

Answer 18

NO. Clinical significance must be assessed by clinician in regard to magnitude of the effect, seriousness of the outcome and prevalance fo the condition.