A teacher has kept tracking of grades and effort put into the class measured by
ID: 3178735 • Letter: A
Question
A teacher has kept tracking of grades and effort put into the class measured by hours studied the day before. The data is shown below:
hours of study Less than 10 10 hours Over 10 Under B 20 18 3 B- to B+ 18 22 25 A- to A+ 6 40 30 a) What is the probability a student will score under a B b) What is the probability a student will score between a B- and B+ c) What is the probability a student will score an A- or above d) If a student scored between B- to B+, what is the probability the student studied over 10 hours?Explanation / Answer
a) Probability that a student will score under a B = total number of student who scored under B/ Total nubmer of students
= ( 20 + 18 + 3) / ( 20 + 18 + 3 +18 + 22 + 25+ 6 + 40 + 30) = 0.225
(b) probability a student will score between a B- and B+ = total number of student who scored between a B- and B+ / Total nubmer of students
= ( 18 + 22 + 25) / ( 20 + 18 + 3 +18 + 22 + 25+ 6 + 40 + 30) = 0.3571
(c) probability a student will score an A- or above =total number of student who scored Above A+ / Total nubmer of students
= (6 + 40 + 30)/( 20 + 18 + 3 +18 + 22 + 25+ 6 + 40 + 30) = 0.4175
(d) here it is conditional probability :
P(student studied over 10 hours if he scored between B- to B+) = students studied over 10 hourse when scored beetween B- to B+/ total number of students got B- to B+ = 25/( 18 + 22+ 25) = 0.3846
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