0

this is a simple example from a statistics textbook that i am a little confused about.

enter image description here

why is the last binomial coefficient 9 choose 7? shouldn't it just be 1? i'm sure that i'm overlooking something simple but i haven't been able to figure it out.

thanks for the help in advance!

1 Answers1

0

It is a typographical error, and indeed should be $\binom 99$.

$$\binom 97 (0.94)^7(0.06)^2+\binom 98 (0.94)^8(0.06)^1+\binom 99(0.94)^9(0.06)^0\approx0.986$$

Graham Kemp
  • 129,094