A random sample of 75 printers discovered that 15 of them were being used in small businesses. find the 90% limit for the population proportion of printers that are used in small businesses.

Sample = 75 printers, Printers used by small businesses = 15

p (15) = 15/75 = 0.2

At 90% limit, Z = 1.64

Limit of proportion of printers used by small business = p + / - Z Sqrt [p (1-p) / n]

=0.2 + / - 1.64 * Sqrt [0.2 (1-0.2) / 75] = 0.2 + / - 0.0757

Limit of proportion = > (0.2-0.0757) to (0.2+0.0757) = > 0.1243 to 0.2757 or 12.43% to 27.57%