Statistics
Two independent samples
April 7, 2009
Outline
1. Situation: a categorical variable with two levels and a quantitative variable
(a) Simple random samples from each of two populations
(b) Simple random sample from one population divided into two groups based on a
categorical variable
(c) Randomized comparative experiment with two treatments
2. Hypothesis tests:
H0 : µ1 = µ2
Ha : µ1 > µ2
H0 : µ1 = µ2
Ha : µ1 < µ2
H0 : µ1 = µ2
Ha : µ1 =
6 µ2
3. If H0 is true, then
x̄1 − x̄2
SE
s
where
SE =
s21
s2
+ 2
n1 n2
has a t-distribution.
Example: Do male and female Calvin students have different body temperatures?
4. Resolving random dot stereograms.
5. Zocor and Vytorin.
http://www.medicalnewstoday.com/articles/39753.php