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Unformatted text preview: how valuable degrees of free dom are when the sample
sizes are small.
Section 9.3
37. Differences of the form (Outdoor – Indoor) hexavalent chromium were calculated, giving
rise to the data in the table. The data are paired by location, so a paired analysis is the
appropriate approach.
a. The confidence interval for D = O – I is given by Indoor
Outdoor
D=OI n
33
33
33 mean
.231
.655
.424 s
.128
.380
.387 . W e are 95% confident that the mean outdoor hexavalent chromium exceeds the mean indoor
value by .287 to .561nanograms/cm 3. b. The prediction error for a newly observed difference (outdoorindoor) in hexavalent chromium is
. The 95% prediction interval for a newly observed difference of outdoor minus indoor hexavalent
chromium is given by
. W e are 95% confident that a newly observed
house would have a difference of outdoor minus indoo r chromium between .376 and 1.224 nanograms/cm3. 38. The sample statistics for peak stress are given in the table.
a. The box plot is given at right. Peak stress has a mild positive skew for the normal
strength mix. Neither box plot indicates strong nonnormality. It’s pretty clear
already what the answer to part (b) will be! The data...
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This note was uploaded on 09/17/2012 for the course STAT 312 taught by Professor Chung during the Spring '04 term at University of Wisconsin.
 Spring '04
 Chung
 Standard Error

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