STAT 3743 Daily Outline
Up there should be four (4) files:

STAT3743_xxxxxx.3gp
(video for mobile phones) 
STAT3743_xxxxxx.ogv
(video in Ogg format) 
STAT3743_xxxxxx.pdf
(scanned lecture transcript) 
STAT3743_xxxxxx.webm
(video in WebM format)
The WebM
video is definitely the highest quality, but
you need a compatible browser/player to watch it.
See How to watch the video for instructions to get one.
PANIC
If σ is unknown, use s instead
Remarks
 if n is large then approx 100(1  α )% confidence
 if n small
– if pop'n normal then use Student's t critical value, get tinterval – if pop'n nonnormal — if approx normal then still not too bad — if highly skewed or outliers, ask statistician
 can have onesided intervals, too
Example: SRS(7) from pop'n, assume norm
, find CI for μ
Confidence intervals for difference of two means
intuition for the confidence interval
First suppose variances known: twosample zinterval
If variances are unknown:
 samples both large: use sample variances, approximate 100(1α )% confidence
 one (or both) samples small, then in trouble unless
– pop'ns both normal — if variances equal: pooled tinterval — variances unequal: Welch interval
Example: independent SRS(4) and SRS(7), norm
Date: 20101105 14:46:42 EDT
HTML generated by orgmode 7.01trans in emacs 23