Probability random variable binomial distribution

Question

Every day, a lecture may be canceled due to inclement weather with probability 0.05. Class cancelations on different days are independent. (a) There are 15 classes left this semester. Compute the probability that at least 4 of them get canceled. (b) Compute the probability that the tenth class this semester is the third class that gets canceled.

How to solve the part b of this question?

score 0 · Accepted Answer · answered Jan 12 '18 at 16:22

0

Hint:

For the tenth class this semester to be the third class that gets cancelled, you want

exactly two of the first nine classes to be cancelled
the tenth class to be cancelled

answered Jan 12 '18 at 16:22

Henry

157,058

Well i tried to construct it like: (9c2 * 1c1)/10c3. Where does that goes wrong? – Satyaki Chatterjee Jan 12 '18 at 17:22
$0.05$ and $0.95$ should appear in the calculation - this involves binomial distributions - while 10c3 should not – Henry Jan 12 '18 at 18:09
(9c1* (.05)^2(1-.05)^7)+(1c1(.05)) is it right..?if not please point out the problem – Satyaki Chatterjee Jan 12 '18 at 18:23
9c2 as you had earlier, but otherwise yes – Henry Jan 12 '18 at 19:49
But still this is not yielding the correct answer (9c2* (.05)^2 * (1-.05)^7)+(1c1*(.05)) .The correct answer is: 0.00314 – Satyaki Chatterjee Jan 13 '18 at 03:53
Multiplication rather than addition, so ${9 \choose 2}\left(\frac{1}{20}\right)^2\left(\frac{19}{20}\right)^7\times {1 \choose 1}\left(\frac{1}{20}\right)^1$ – Henry Jan 13 '18 at 09:26

Probability random variable binomial distribution

1 Answers1