Easy -1.2 This is a straightforward application of a two-stage tree diagram with given probabilities and basic probability calculations using the law of total probability. It requires only routine recall of tree diagram construction and simple arithmetic (0.85×0.97 + 0.15×0.94), making it easier than average for A-level.
4. A company assembles drills using components from two sources. Goodbuy supplies the components for \(85 \%\) of the drills whilst Amart supplies the components for the rest.
It is known that \(3 \%\) of the components supplied by Goodbuy are faulty and \(6 \%\) of those supplied by Amart are faulty.
a Represent this information on a tree diagram.
An assembled drill is selected at random.
b Find the probability that the drill is not faulty.
4. A company assembles drills using components from two sources. Goodbuy supplies the components for $85 \%$ of the drills whilst Amart supplies the components for the rest.\\
It is known that $3 \%$ of the components supplied by Goodbuy are faulty and $6 \%$ of those supplied by Amart are faulty.\\
a Represent this information on a tree diagram.
An assembled drill is selected at random.\\
b Find the probability that the drill is not faulty.\\
\hfill \mbox{\textit{SPS SPS SM Statistics 2021 Q4 [4]}}