I
noun
BAD : The average of hours spent watching television has increased.
GOOD : The average number of hours spent watching television has increased.
GOOD : The average hours spent watching television have increased.
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an/the average of + NUMBER: 'The average of 3, 4 and 8 is 5.' 'The test results produced an average of 65 per cent.'
the average number/amount/level/age of + NOUN: 'The average age of the children is five years and seven months.'
an/the average + NOUN: 'The average salary is $2100 a month.'
II
adjective
BAD : The article was about average British people and their reluctance to learn foreign languages.
GOOD : The article was about typical British people and their reluctance to learn foreign languages.
BAD : The Los Angeles Medical Centre announced that the average AIDS patient requires about two to three months of hospitalization.
GOOD : The Los Angeles Medical Centre announced that the typical AIDS patient requires about two to three months of hospitalization.
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average = not special or unusual in any way; of the usual standard or level: 'Anyone of average intelligence knows that drugs are dangerous.' 'The average student takes about two hours to complete the test.'
typical = having the same appearance, behaviour or characteristics as a particular type of person or thing: 'McGarron looked like a typical American car salesman.' 'John's wife is a typical teacher.'