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    a teacher travels from home by car each weekday. her journey times are normally distributed with a mean of 30.4 mins and a standard deviation of 3.6 mins. calculate the probability that her journey time on a particular day takes between 25 minutes and 35 minutes.

    ive standardised and got p(-1.5<z<1.28), where do i go next?
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    (Original post by shubhondeb)
    a teacher travels from home by car each weekday. her journey times are normally distributed with a mean of 30.4 mins and a standard deviation of 3.6 mins. calculate the probability that her journey time on a particular day takes between 25 minutes and 35 minutes.

    ive standardised and got p(-1.5<z<1.28), where do i go next?
    Draw a bell curve and consider the region you need to find.

    Are you doing old (modular) spec or new spec? The method you use depends on this.
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    To find the relevant area of the Normal Distribution note:

     P( a \, &lt; \, z \, &lt; \, b ) = P(z &lt; b) - P(z &lt; a), using tables to find P(a) and P(a).

    Also do you know how to deal with "P(a)" where a is negative?

    Spoiler:
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    P(-n) = 1 - P(n), where "-n" is a negative value (using symmetry).




    Can you take it forward from here?
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    (Original post by Notnek)
    Draw a bell curve and consider the region you need to find.

    Are you doing old (modular) spec or new spec? The method you use depends on this.
    old spec s1
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    (Original post by simon0)
     P( a \, &lt; \, z \, &lt; \, b ) = P(b) - P(a), using tables to find P(a) and )(a).

    Can you take it forward from here?
    Ah i see, thank you!
 
 
 
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