find the value of normal distribution with a 3 decimal places Z score using table












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In a past exam of my stats class, the question requires finding the value of a normal CDF corresponding to a Z score of 3 DP. However, we are only given a table that is accurate to 2 DP. We are not allowed to use calculator. What should I do to find the value when the Z score is 1.293, not just 1.29.










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  • $begingroup$
    You can linearly interpolate the values for $1.29$ and $1.3$
    $endgroup$
    – lulu
    Dec 29 '18 at 0:34












  • $begingroup$
    Would linear interpolation be accurate enough? If so using $1.29, 1.30$ and cutting three tenths between would be a possible way.
    $endgroup$
    – coffeemath
    Dec 29 '18 at 0:35


















0












$begingroup$


In a past exam of my stats class, the question requires finding the value of a normal CDF corresponding to a Z score of 3 DP. However, we are only given a table that is accurate to 2 DP. We are not allowed to use calculator. What should I do to find the value when the Z score is 1.293, not just 1.29.










share|cite|improve this question









$endgroup$












  • $begingroup$
    You can linearly interpolate the values for $1.29$ and $1.3$
    $endgroup$
    – lulu
    Dec 29 '18 at 0:34












  • $begingroup$
    Would linear interpolation be accurate enough? If so using $1.29, 1.30$ and cutting three tenths between would be a possible way.
    $endgroup$
    – coffeemath
    Dec 29 '18 at 0:35
















0












0








0





$begingroup$


In a past exam of my stats class, the question requires finding the value of a normal CDF corresponding to a Z score of 3 DP. However, we are only given a table that is accurate to 2 DP. We are not allowed to use calculator. What should I do to find the value when the Z score is 1.293, not just 1.29.










share|cite|improve this question









$endgroup$




In a past exam of my stats class, the question requires finding the value of a normal CDF corresponding to a Z score of 3 DP. However, we are only given a table that is accurate to 2 DP. We are not allowed to use calculator. What should I do to find the value when the Z score is 1.293, not just 1.29.







normal-distribution






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asked Dec 29 '18 at 0:27









ZeyuanZeyuan

1273




1273












  • $begingroup$
    You can linearly interpolate the values for $1.29$ and $1.3$
    $endgroup$
    – lulu
    Dec 29 '18 at 0:34












  • $begingroup$
    Would linear interpolation be accurate enough? If so using $1.29, 1.30$ and cutting three tenths between would be a possible way.
    $endgroup$
    – coffeemath
    Dec 29 '18 at 0:35




















  • $begingroup$
    You can linearly interpolate the values for $1.29$ and $1.3$
    $endgroup$
    – lulu
    Dec 29 '18 at 0:34












  • $begingroup$
    Would linear interpolation be accurate enough? If so using $1.29, 1.30$ and cutting three tenths between would be a possible way.
    $endgroup$
    – coffeemath
    Dec 29 '18 at 0:35


















$begingroup$
You can linearly interpolate the values for $1.29$ and $1.3$
$endgroup$
– lulu
Dec 29 '18 at 0:34






$begingroup$
You can linearly interpolate the values for $1.29$ and $1.3$
$endgroup$
– lulu
Dec 29 '18 at 0:34














$begingroup$
Would linear interpolation be accurate enough? If so using $1.29, 1.30$ and cutting three tenths between would be a possible way.
$endgroup$
– coffeemath
Dec 29 '18 at 0:35






$begingroup$
Would linear interpolation be accurate enough? If so using $1.29, 1.30$ and cutting three tenths between would be a possible way.
$endgroup$
– coffeemath
Dec 29 '18 at 0:35












1 Answer
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$begingroup$

Personally, I would just round to $1.29$. However, if you really want to guess $text{normalcdf}(1.293)$, I would just do a weighted sum.



First, write $1.293$ in terms of $1.29$ and $1.30$, since those are the two-decimal z-scores closest to it:



$$1.293=0.7cdot 1.29+0.3cdot 1.30$$



Then, pretend $text{normalcdf}$ is linear:



$$text{normalcdf}(1.293)=0.7text{normalcdf}(1.29)+0.3text{normalcdf}(1.30) \ =0.7cdot 0.9015+0.3cdot 0.9032=0.90201$$






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    $begingroup$

    Personally, I would just round to $1.29$. However, if you really want to guess $text{normalcdf}(1.293)$, I would just do a weighted sum.



    First, write $1.293$ in terms of $1.29$ and $1.30$, since those are the two-decimal z-scores closest to it:



    $$1.293=0.7cdot 1.29+0.3cdot 1.30$$



    Then, pretend $text{normalcdf}$ is linear:



    $$text{normalcdf}(1.293)=0.7text{normalcdf}(1.29)+0.3text{normalcdf}(1.30) \ =0.7cdot 0.9015+0.3cdot 0.9032=0.90201$$






    share|cite|improve this answer









    $endgroup$


















      1












      $begingroup$

      Personally, I would just round to $1.29$. However, if you really want to guess $text{normalcdf}(1.293)$, I would just do a weighted sum.



      First, write $1.293$ in terms of $1.29$ and $1.30$, since those are the two-decimal z-scores closest to it:



      $$1.293=0.7cdot 1.29+0.3cdot 1.30$$



      Then, pretend $text{normalcdf}$ is linear:



      $$text{normalcdf}(1.293)=0.7text{normalcdf}(1.29)+0.3text{normalcdf}(1.30) \ =0.7cdot 0.9015+0.3cdot 0.9032=0.90201$$






      share|cite|improve this answer









      $endgroup$
















        1












        1








        1





        $begingroup$

        Personally, I would just round to $1.29$. However, if you really want to guess $text{normalcdf}(1.293)$, I would just do a weighted sum.



        First, write $1.293$ in terms of $1.29$ and $1.30$, since those are the two-decimal z-scores closest to it:



        $$1.293=0.7cdot 1.29+0.3cdot 1.30$$



        Then, pretend $text{normalcdf}$ is linear:



        $$text{normalcdf}(1.293)=0.7text{normalcdf}(1.29)+0.3text{normalcdf}(1.30) \ =0.7cdot 0.9015+0.3cdot 0.9032=0.90201$$






        share|cite|improve this answer









        $endgroup$



        Personally, I would just round to $1.29$. However, if you really want to guess $text{normalcdf}(1.293)$, I would just do a weighted sum.



        First, write $1.293$ in terms of $1.29$ and $1.30$, since those are the two-decimal z-scores closest to it:



        $$1.293=0.7cdot 1.29+0.3cdot 1.30$$



        Then, pretend $text{normalcdf}$ is linear:



        $$text{normalcdf}(1.293)=0.7text{normalcdf}(1.29)+0.3text{normalcdf}(1.30) \ =0.7cdot 0.9015+0.3cdot 0.9032=0.90201$$







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        share|cite|improve this answer



        share|cite|improve this answer










        answered Dec 29 '18 at 0:36









        Noble MushtakNoble Mushtak

        15.3k1835




        15.3k1835






























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