A web based software company is interested in estimating the proportion of individuals who use the Firefox browser. In a sample of 200 of individuals, 19 users stated that they used Firefox. Using this data, construct a 99% confidence interval for the proportion of all individuals that use Firefox.

confidence interval = (8.33%; 10.67%) equivalent to (16.67 people; 21.34 people)

9.5% + / - 1.17%

Explanation:

X = the proportion of people who use the Firefox

p = 19/200 = 0.095

z = 2.575

(p - z x √ (p x (1 - p) / population) < p < (p + z x √ (p x (1 - p) / population)

(0.095 - {2.575 x (0.905/200) < p < (0.095 + {2.575 x (0.905/200)

(0.095 - 0.0117) < p < (0.095 + 0.0117)

0.0833 < p < 0.1067