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

A school's administrators are concerned about absenteeism at their school

and the eect 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?

2/19

e. What is the probability that a randomly selected student has either high grade or absent frequently?

I don't know how to calculate this

- probabilityv -
**PsyDAG**, Saturday, October 16, 2010 at 11:31am
a. total of low grade students/grand total of students = 18/85

b. total of frequently absent students/grand total of students

c. Yes,try a Chi-squared (X^2) test to show why

d. Yes!

e. Either-or probabilities are found by adding the probabilities of the individual events. Total number of high grade/grand total + total number of absent frequently/grand total

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