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Computer disc media

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Keywords:
computer; CD; DVD; disc; disk; price
Categories:
regression;
popular
Description:
The price of CDs, DVD-Rs and DVD+/-RWs were obtained from a Choice magazine study of reliability of computer media. The discs were purchased by Choice magazine in April 2005 in multi-packs (the small number of individual purchases of discs were discarded). The brand names, though reported by Choice, are not given.

There are 28 observations on three variables.

Variables:
price The price per disc in Australian dollars paid by Choice in April 2005
pack The pack size: the number of disc in the pack
media The type of media: one of CD (CD), DVD (DVD-R) or DVDRW (DVD+/-RW)
Data Quality:
There are no missing values.
Source:
Choice magazine webpage, accessed 28 July 2005.
Notes:
One can fit a regression model. media is, unsurprisingly, highly significant, pack mildly significant, and the interaction (perhaps surprisingly) insignificant. The main lesson is in interpretation: what do the intercept and slope mean? How can they be interpretted? A residual plot shows heteroscedasticity; a log transform (or gamma glm) seems necessary.
References: