January 31, 2015

Homework Help: probabilityv

Posted by lisa on Saturday, October 16, 2010 at 2:17am.

A school's administrators are concerned about absenteeism at their school
and the e ect it has on students' grades. The following data were compiled, based on a sample of students.
Student's Absent Medium Absent
Grade Infrequently Absent Frequently
Low 1 9 8
Medium 6 35 7
High 8 9 2
a. What is the probability that a randomly selected student will have a low grade?

This would be 1/15 + 9/53 + 8/17 right?

b. What is the probability that a randomly selected student absent frequently?

8/18 + 7/48 + 2/19

c. Are grades and frequency in absent independent events? Why?

Not sure but i think they are dependent

d. Knowing that a randomly selected student has high grade, what is the probability that student is absent frequently?
e. What is the probability that a randomly selected student has either high grade or absent frequently?
I dont know how to calculate this

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