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    Hi everyone, I have just started the normal approximations topic for S2 edexcel maths and for some reason on each different resource I have (I use exam solutions, my text book and other online notes etc) each is telling me different things about continuity correction. I am unsure whether or not to add 0.5 or subtract it when you have different probabilities which include bigger(or smaller) and equal to/ bigger (or smaller) than X. And whether or not to use <_ when you change it to a continuous or if it must be just < as in continuous PROBABILITY =X is 0. I hope this makes sense x I would really appreciate if someone could clear up what I am confused about xx thanks so much

    (If perhaps someone could just tell me the rules that may be the easiest way, )
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    (Original post by biohalle)
    Hi everyone, I have just started the normal approximations topic for S2 edexcel maths and for some reason on each different resource I have (I use exam solutions, my text book and other online notes etc) each is telling me different things about continuity correction. I am unsure whether or not to add 0.5 or subtract it when you have different probabilities which include bigger(or smaller) and equal to/ bigger (or smaller) than X. And whether or not to use <_ when you change it to a continuous or if it must be just < as in continuous PROBABILITY =X is 0. I hope this makes sense x I would really appreciate if someone could clear up what I am confused about xx thanks so much

    (If perhaps someone could just tell me the rules that may be the easiest way, )
    You are, in essence, replacing a point value with an interval.

    E.g X=4, is replaced with X in the interval [4-0.5, 4+0.5] = [3.5,4.5]

    So, with a strict inequality, X>4, now becomes X > everything in the interval (or less), i.e. X>4.5

    Similarly X<4 becomes X<3.5

    With a weak inequality X>=4, this includes the possibility that X=4, so we include the interval and this becomes X>=3.5

    Similarly X<=4, becomes X<=4.5.

    Whether you use X<=4.5 or X<4.5 doesn't matter for a continuous distribution. I'd go with what the original inequality was, strict or weak.
 
 
 
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