Statistical Statistical VariablesVariables

Supervisied by:Supervisied by:Professor Samer Roustom, Professor Samer Roustom,

M.D.M.D.Sara Oubari & Laila NourSara Oubari & Laila Nour

Statistical Statistical VariablesVariables

If Epidemiology is about understanding the world in terms of RatiosStatistics is about understanding the world in terms of Distributions

Interferential Statistics bulids a bridge between the sample and the

population

Interferential Statistics bulids a bridge between the sample and the

population

instead of proving our hypothesis, we just try to prove that all of the

alternatives are wrong

Patients with elevated plasma creatinine or Patients with elevated plasma creatinine or

RRT had an annual death rate of 19.2% RRT had an annual death rate of 19.2% (95% (95% confidence interval, CI, 14.0 to 24.4%). confidence interval, CI, 14.0 to 24.4%). There There

was a trend for increasing risk of was a trend for increasing risk of cardiovascular death with increasing cardiovascular death with increasing

nephropathy nephropathy (P < 0.0001)(P < 0.0001)

Absolute risk

Relative risk (RR)

Cohort studies

Relative risk (RR)• RR = 1 No difference in risk

• RR < 1 Exposed < Unexposed

• RR > 1 Unexposed < Exposed

• Relative risk reduction

Odds Ratio(OR)

Case-Control studies

Smoking Lung Cancer TotalYes No

Yes 30 170 200No 5 995 1000

Total 35 1165 1200

Risk for smokers = 30/200 = 0.15Risk for nonsmokers = 5/1000 = 0.005Relative risk (RR) = 0.15/0.005 = 30

Odds for smokers = 30/170 = 0.176 Odds for nonsmokers = 5/995 = 0.005 Odds ratio (OR) = 0.176/0.005 = 35.1

Flavonol V.S CHDComparison of individuals in the top third with

those in the bottom third of dietary flavonol intake yielded a combined risk ratio of 0.80 (95% CI 0.69–0.93) after adjustment for known CHD risk factors

and other dietary components.

Maternal dietary supplements and language delayAdjusted ORs for 3 patterns of exposure to maternal dietary supplements were (1) other supplements, but no folic acid (n = 2480 [6.6%], with severe

language delay in 22 children [0.9%]; OR, 1.04; 95% CI, 0.62-1.74); (2) folic acid only (n = 7127 [18.9%], with severe language delay in 28 children

[0.4%]; OR, 0.55; 95% CI, 0.35-0.86); and (3) folic acid in combination with other supplements (n = 19 005 [50.5%], with severe language delay in 73

children [0.4%]; OR, 0.55; 95% CI, 0.39-0.78).