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Table 3 Results of t-tests and descriptive statistics on the percentage of failed sheets within an inventory number grouped by the type of protective enclosures, (A) including all observations and (B) including only inventory numbers containing more than 100 sheets

From: Accumulation of wear and tear in archival and library collections. Part II: an epidemiological study

Exposure variable Outcome variable: failed sheets (%) n 95% CI for mean difference t df p
M SD SE
(A) Portfolio 21.9 21.2 2.2 94 − 8.6, 6.8 − 0.24 155 0.812
 Box 22.9 30.2 3.2 88
(B) Portfolio (> 100 sheets) 25.2 17.1 2.5 46 1.3, 15.5 2.37 88 0.020
 Box (> 100 sheets) 17.7 16.8 2.5 45
  1. M, mean; SD, standard deviation; SE, standard error of the mean; n, number of observations; CI, confidence interval; t, t test; df, degrees of freedom; p, p-value