Standardised deviation test

Discussion in 'CS2' started by Aisha, May 14, 2019.

  1. Aisha

    Aisha Very Active Member

    In solutions for chapter 10 practice questions, Q10.10(iii) , under ISD test, it's given that the distribution is positively skewed, which is not so good.
    How did we come to a conclusion that it is positively skewed?
    Also while we talk about symmetry, we tend to look at the number of positive and negative deviations which are 5 and 4 respectively in this case, so from this can't we conclude that it is fairly symmetrical?
     
  2. Andrew Martin

    Andrew Martin ActEd Tutor Staff Member

    Hi Aisha

    We can consider both how many positive and negatives there are as well as the magnitudes of the deviations. Although there are similar counts (5 and 4 as you say), the negative ones are all in the (-1,0) range, where as the positive ones are somewhat spread from 0 to 3. We know that a normal distribution has symmetry in the magnitudes as well as the counts. This is also the same observation that leads to the conclusion of positive skew.

    Andy
     
    Aisha likes this.
  3. Aisha

    Aisha Very Active Member

    Understood. Thank you!

     

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