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    Hi can someone explain why E(X) is 2 here? The answers at the back say its 2 because its symmetrical but I dont understand? Name:  ImageUploadedByStudent Room1456424710.785223.jpg
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    (Original post by jessyjellytot14)
    Hi can someone explain why E(X) is 2 here? The answers at the back say its 2 because its symmetrical but I dont understand? Name:  ImageUploadedByStudent Room1456424710.785223.jpg
Views: 67
Size:  132.8 KB


    Posted from TSR Mobile
    Well, it's because symmetry. But another way to see it is:

    E(X) = a + 2b + 3a = 4a + 2b = 2(2a+b)

    But you know that probabilities sum to one, so: a + b + a = 1 = 2a +b, back-subbing:

    E(X) = 2(2a +b) = 2(1) = 2.
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    (Original post by Zacken)
    Well, it's because symmetry. But another way to see it is:

    E(X) = a + 2b + 3a = 4a + 2b = 2(2a+b)

    But you know that probabilities sum to one, so: a + b + a = 1 = 2a +b, back-subbing:

    E(X) = 2(2a +b) = 2(1) = 2.
    no full solutions!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!
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    (Original post by aymanzayedmannan)
    no full solutions!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!
    :rofl:
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    (Original post by jessyjellytot14)
    Hi can someone explain why E(X) is 2 here? The answers at the back say its 2 because its symmetrical but I dont understand? Name:  ImageUploadedByStudent Room1456424710.785223.jpg
Views: 67
Size:  132.8 KB


    Posted from TSR Mobile
    The x values either side of 2 are the same distance from 2 and have the same probability. That is the symmetry that they are talking about.
 
 
 
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