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(Binary Independence Model) Consider the following document-term matrix, where a

ID: 3686239 • Letter: #

Question

(Binary Independence Model) Consider the following document-term matrix, where a 1 entry indicates that the term occurs in a document, and 0 means it does not: Assume that the number of non-relevant documents is approximated by the size of the collection and that the probability of occurrence in relevant documents is constant over all the terms in the query (specifically, p_i = 0.9). For each of the following queries, rank the documents in decreasing order of relevance. q1 = {t1, t2} q2 = {t3} q3 = {t2, t4}

Explanation / Answer

Example:

doc1 = d1 = “The quick fox jumped over the fence”

doc2 = d2 = “She likes the Bass is it the fish bass the music frequency bass”

d3 = “The farmer laid the fence around the apple farm”

d4 = “An apple a day keeps the doctor away”

matrix:

The

quick

fox

jumped

over

fence

She

likes

bass

is

it

fish

music

frequency

farmer

laid

around

apple

farm

an

a

day

keeps

away

doctor

d1

2

1

1

1

1

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

d2

3

0

0

0

0

0

1

1

3

1

1

1

1

1

0

0

0

0

0

0

0

0

0

0

0

d3

3

0

0

0

0

1

0

0

0

0

0

0

0

0

1

1

1

1

1

0

0

0

0

0

0

d4

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1

0

1

1

1

1

1

1

Example:

doc1 = d1 = “The quick fox jumped over the fence”

doc2 = d2 = “She likes the Bass is it the fish bass the music frequency bass”

d3 = “The farmer laid the fence around the apple farm”

d4 = “An apple a day keeps the doctor away”

matrix:

The

quick

fox

jumped

over

fence

She

likes

bass

is

it

fish

music

frequency

farmer

laid

around

apple

farm

an

a

day

keeps

away

doctor

d1

2

1

1

1

1

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

d2

3

0

0

0

0

0

1

1

3

1

1

1

1

1

0

0

0

0

0

0

0

0

0

0

0

d3

3

0

0

0

0

1

0

0

0

0

0

0

0

0

1

1

1

1

1

0

0

0

0

0

0

d4

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1

0

1

1

1

1

1

1

The

quick

fox

jumped

over

fence

She

likes

bass

is

it

fish

music

frequency

farmer

laid

around

apple

farm

an

a

day

keeps

away

doctor

d1

2

1

1

1

1

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

d2

3

0

0

0

0

0

1

1

3

1

1

1

1

1

0

0

0

0

0

0

0

0

0

0

0

d3

3

0

0

0

0

1

0

0

0

0

0

0

0

0

1

1

1

1

1

0

0

0

0

0

0

d4

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1

0

1

1

1

1

1

1