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Size:  88.6 KBCan someone tell me why for question d) you do the sum p(x<_7)-p(x<_1) as opposed to using p(x<2) thankyou
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    (Original post by Abby5001)
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Size:  88.6 KBCan someone tell me why for question d) you do the sum p(x<_7)-p(x<_1) as opposed to using p(x<2) thankyou
    P(x <=1) = P(x<2) since the binomial is a discrete distribution; x can only be an integer so saying x is less than 2 means x must be 1 or 0.
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    (Original post by 16Characters....)
    P(x <=1) = P(x<2) since the binomial is a discrete distribution; x can only be an integer so saying x is less than 2 means x must be 1 or 0.
    I understand what you are saying but x is not less than 2 according to the signs surely? It's less than or equal to?
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    (Original post by Abby5001)
    I understand what you are saying but x is not less than 2 according to the signs surely? It's less than or equal to?
    I apologise, my response was clumsily worded.

    You are finding P(2 <= x <= 7) so you are finding the probability that x = 2, 3, 4, 5, 6, or 7. P(x <=7) finds the probability that x = 0, 1, 2, 3,..., 7 which is including the values of x less than 2, which you did not want. So you subtract P(x < 2). Which is equivalent to P(x <= 1).
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    (Original post by 16Characters....)
    I apologise, my response was clumsily worded.

    You are finding P(2 <= x <= 7) so you are finding the probability that x = 2, 3, 4, 5, 6, or 7. P(x <=7) finds the probability that x = 0, 1, 2, 3,..., 7 which is including the values of x less than 2, which you did not want. So you subtract P(x < 2). Which is equivalent to P(x <= 1).
    Right thankyou that was very helpful but what is the reason why x<_1 is used rather than x<2?
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    (Original post by Abby5001)
    Right thankyou that was very helpful but what is the reason why x<_1 is used rather than x<2?
    Well you could have used either, they are as I said equivalent probabilities. I suspect P(x <=1) is used as it is clearer what you are actually doing, especially if you are using the cumulative probability tables.
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    (Original post by 16Characters....)
    Well you could have used either, they are as I said equivalent probabilities. I suspect P(x <=1) is used as it is clearer what you are actually doing, especially if you are using the cumulative probability tables.
    great I see, thanks again
 
 
 
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