Therefore, the Age variable is a categorical variable. In a study, the age information was collected in terms of the following age categories. Therefore, the Age variable is a categorical variable. AGE Percentage 20 to less than 30 23% 30 to less than 40 30% 40 to less than 50 35% 50 to less than 60 10% 60 and above 2% Yes or No

There is significant correlation between treatment and outcome. Observational study: results from 2 treatment levels (different dosages) and their outcomes. (Data from 200 randomly selected patients.) Hypertension Treatment Yes No Total A: 250mg 44 56 100 B: 500mg 29 71 73 127 200 Treatment A: 44/100 = 44% Treatment B: 29/100 = 29% There is significant correlation between treatment and outcome.

So, lower dosage was the cause of the higher rate of hypertension. Your Answer: Yes or No Association does not imply causation

Hypertension Below 65 65+ Treatment Yes No Total A 5 18 23 39 38 77 B Multivariate approach in data analysis Hypertension Below 65 65+ Treatment Yes No Total A 5 18 23 39 38 77 B 17 60 12 11 * Older patients prefer Drug A OR <65: A: 5/23 = 22% B: 17/77 = 22% OR 65+: A: 39/77 = 51% B: 12/23 = 52%

Two Quantitative variables Average annual temperature and the mortality index for breast cancer in women in certain region of Europe.

Since there is very clear upward linear trend, so can we conclude that the high temperature increased the mortality index? Your Answer: Yes or No

When a person’s height is 45 inches, the expected weight for the person’s would be around 40 lbs. Yes or No

Confidence interval with z-score: The (1 a)% confidence interval estimate for population mean: Assumption: If sampled from normal population with known variance, s,  Assumption: If large sample and if unknown variance, s replaces s, Rarely used in practice!

“The” Method Used in Practice Confidence interval with t-score: The (1 a)% confidence interval estimate for population mean: Assumption: If sampled from normal population with unknown variance, s,  (If sample size is large the normality assumption is insignificant.) t  z as sample becomes large

t-Test Statistic for testing Mean p-value is the common approach

Student’s t Distribution Z Standard Normal (Z) Bell-Shaped Symmetric ‘Fatter’ Tails t (df = 13) t (df = 5) t