Number of Pages in a Science Review Book

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Sometimes we wonder if we are getting our money's worth for the review books we buy. The prices and number of pages (xls) of randomly sampled Advanced Placement, SAT II, New York State Regents and other review books in Physics, Chemistry and Biology were taken. Linear regression analyses were done to determine of there is any significance between the price of the book and the number of pages it has. The regression t-test of each category was calculated on a TI-83 graphing calculator. These are following regressions for the respective categories.

Regents	Advanced Placement	SAT II	Other
y = 80.107 + 36.497 x	y = 377.405 + 1.2155 x	y = 132.529 + 14.145 x	y = 215.00 + 7.1 x
r² = .5176	r² = 8.03 × 10⁻⁴	r² = .1056	r^2 = .070
r = .7188	r = .0283	r = .3249	r = .2647
t = 3.269	t = .1146	t = 1.4578	t = 1.841
p = .0084	p = .886	p = .1621	p = .0722
df = 10	df = 26	df = 16	df = 45

Using an alpha level of 5%, just the Regents review have a significant slope. We can say that for the Regents review books, 71.88% of the change in the price is accounted for by the number of pages. The other 28.12% of change is due to either chance error or some outside variable that is not included in the linear relationship. Since there is a small degree of freedom, we cannot trust this result. The other review books show us that there is absolutely no significant correlation between the cost of the book and the number of pages in it. All of the data was combined and another linear regression t-test was done.

All Review Books
y = 276.46 + 5.826 x
r² = .0399
r = .1842
t = 1.921
p = .05746
df = 105

Again, with all of the combined data, we can see that there is no correlation between the number of pages and the cost of the review books. We cannot determine if our money is well spent.

Samantha Dong -- 2002

Data and Story Project