# statistics , question 5, grade 10

12/11/2017

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

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

[

- σ,

+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.