I'm taking a course in probability and statistics and encountered an exercise with a formulation that doesn't make sense at all to my English-as-second-language ears.

I will recite the exercise here and maybe you could help my settle wether if the original formulation is bad, or if I've found an opportunity to learn a new way of formulating myself in English.

The exercise is from "Introduction to Probability and Statistics" by J.Susan Milton and Jesse C. Arnold (McGraw-Hill 2004).

I'll quote some excerpts that I think will provide enough information.

Section 3.4, ex. 25:

The density function is given by

f(x) = (1-p)^{x-1}*p (geometric)

where p=.05

Now (e) doesn't make any sense at all to me. What makes least sense is the use of "that".

It's solved by

P(X≥3) = 1-( f(1) + f(2) )

However, a more appropriate formulation of (e) I then think would be for instance:

What do you think? Is the original formulation of (e) good, quite inprecise or even incorrect?

It means, 2 runs produce no unacceptable lots. Therefore you need at least 3 to produce an unacceptable lot. So you want the probability p that the first 2 runs are acceptable.