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    Hi,

    Can someone confirm i have done the right thing and just check my answer ?

    My question was what percentage of animals should be between 15cm and 20.5cm in length? (normal distribution) using cummulative normal probability table

    mean = 18cm sd= 2cm

    using the formula i calculated the z value of 15cm to be -1.5 and z value of 20.5cm to be 1.25. Then I looked up in the table to find the p values, which are :

    z=-1.5 (p 0.06681)
    z=1.25 (p 0.89435)

    and then my conclusion: 0.06% of animals should be between 15cm and 0.89% of animals should be between 20.5.

    Now i m not sure if this is correct or not, anyone done statistics here ? please look at this and let me know as i dont want to do the wrong thing in my test
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    (Original post by Gamewizard)
    and then my conclusion: 0.06% of animals should be between 15cm and 0.89% of animals should be between 20.5.

    Now i m not sure if this is correct or not, anyone done statistics here ? please look at this and let me know as i dont want to do the wrong thing in my test
    What?! Read your own conclusion - it makes no sense!! "Between 15"? Between 15 and what?

    What you actually know from your calculation is:
    6.681% of animals should be less than 15cm long
    89.435% of animals should be less than 20.5cm long

    So you can conclude (and sketching the graph for this to visualise it might help) that:
    89.435% - 6.681% = 82.754% of animals should be between 15cm and 20.5cm long
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    (Original post by tomthecool)
    What?! Read your own conclusion - it makes no sense!! "Between 15"? Between 15 and what?

    What you actually know from your calculation is:
    6.681% of animals should be less than 15cm long
    89.435% of animals should be less than 20.5cm long

    So you can conclude (and sketching the graph for this to visualise it might help) that:
    89.435% - 6.681% = 82.754% of animals should be between 15cm and 20.5cm long
    Oh right sorry yes read it again, it didnt make sense. Ah damn so my answer was wrong then.

    Thank you
 
 
 
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