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Statistics - Probability Help!

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    How do you calculate this:

    Three MPs were selected at random for a committee. Calculate, to three decimal places, the probability that exactly one MP was Labour and exactly one MP was Conservative?

    ............ Labour ....... Conservative ........ Lib Dem .......... Other .......... Total
    Male ........ 225 .......... 175 .................. 54 .............. 35 ............. 519
    Female ....... 94 .......... 18 .................... 9 ................. 5 .............. 126
    Total ....... 349 .......... 193 ................. 63 ................ 40 .................. 645
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    Think of the combinations you could have (L & C & oneOther), then (C & L & oneOther). How many different combinations could you have?

    So in the first combination the probability is (349/645 x 193/644 (you've one less to choose from) x 103/643(now 2 less to choose from)).

    You could look at each different combination and work those out too and then add them together. BUT before doing that, just write down what you'll be working out and see if you can spot a pattern you should see something that will be a time saver.

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Updated: May 3, 2013
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