Question

Internet sites often vanish or move so that references to them cannot be followed. In fact, 13% of Internet sites referenced in major scientific journals are lost within two years after publication. If a paper contains nine Internet references, what is the probability that all nine are still good two years later? Round your answer to three decimal places. What specific assumption must be made in order to calculate the probability? The paper containing the references must be obtained by random sampling. The occurrence of the site references in the paper are independent events. The occurrence of the site references in the paper are disjoint events, One does not need to make any assumptions; this is just a straightforward calculation. P(all nine are still good)=

Answer 1

Answer:

The probability that all nine references are still good two years later is P(all nine are still good)=0.29.

The assumption we have to make is that the occurrence of the site references in the paper are independent events.

Step-by-step explanation:

The assumptions we have to make about the papers is that their probabilities of survival are independent of each other. This is the same as saying: The occurrence of the site references in the paper are independent events.

The probabilities of survival of any reference is:

$P(survive)=1-P(lost)=1-0.13=0.87$

The probability of the nine references are still good later can be calculated as:

$P=\prod_{k=1}^{9}P(x_k=S)=P(x=S)^9=0.87^9=0.29$

The probability that all nine references are still good two years later is P=0.29.