Math Is Fun Forum

pinkdiva

Member

Registered: 2008-08-05

Posts: 1

data question

look this question might seem really easy but i am not particularly good at data and that stuff.

Age Frequency
15-29 470
30-44 165
45-59 93
Total 728

How do you work out the:
mean
median

please help me

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: data question

For this question, you need to assume that the ages are distributed evenly within each age range.
With this assumption, the mean of the ages within each range would be that range's midpoint.

Therefore, the total of all the ages would be 470*22 + 165*37 + 93*52 = 21281.
There are 728 people in total, so their mean age is 21281/728 ≈ 29.2

To find the median age, first work out what range it would be in. The median person would be the 364th person when they are arranged in ascending order, and so they would be in the 15-29 range.

Now work out "how far in" the person is into that range, and use that to estimate the age.
Of the 470 people who are 15-29, the median is the 364th. The range of the group is 14 years.

Therefore, that person's age is roughly 15 +  14*(364/470) = 25.8

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Why did the vector cross the road?
It wanted to be normal.