Question

Suppose that 30% of students prefer to write with a mechanical pencil. suppose we sample students, one at a time, and stop as soon as we have selected one who prefers to write with a mechanical pencil. the probability that we will select 2 or fewer students is

Answer 1

Probability that first student  prefers mechanical pen = 0.30
 P(first student does not and second student does) = 0.70 * 0.3 =  0.21)

P( selecting 2 or fweer) = 0.30+ 0.21) = 0.51  or 51%