# statistics, question 1, grade 10

1)

A teacher examined 25 students in math and gave the results arranged in the following table:

grades (xi) | 10 | 13 | 15 | 18 | 20 | total |

frequency (ni) | 3 | x | y | 5 | 2 | 25 |

- Calculate x and y knowing that 17 students got at least 15 andĀ the class average was 15
- Suppose in what follows that x=5 and y=10

a) Determine the mode and the median.

b) Use the calculator to find the standard deviationĀ

c) Find the percentage of students whose grades belong to the given set: