statistics , question 5, grade 10

12/11/2017 Grade 10 5,146

5)

  1. After a survey done on the ages of 50 children on their first day at a scouts’ camp, the results were shown in the following table:
Ages 7 9 10 12 Total
n0” of chidren 10 15 20 5 50

 

  • Calculate the mean

    \overlineX

    and the standard deviation σ.
  • Find the number of children whose ages belong to the set:

[

\overlineX

- σ, 

\overline X

+σ ]U{12}.

  • That day, a competition was held and only children whose ages are at least 10 can participate, find the percentage of those who can participate.
  • On the second day, a group of 12 years old children joined the camp and the mean age becomes 11, find the number of these children.