Math Is Fun Forum

EbenezerSon

Member

Registered: 2013-07-04

Posts: 554

About Statistics

I'm a little bit bemused about the difference between grouped and ungrouped data.
Does a grouped data always have class intervals such as 0-9, 10-19...? Whiles an ungrouped data does not have such class intervals?
Please confirm, thank you in advance

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I know only one thing - that is that I know nothing

Bob

Administrator

Registered: 2010-06-20

Posts: 10,619

Re: About Statistics

hi EbenezerSon

These would be ungrouped:

3, 5, 6, 17, 23, 24, 33, 10, 6, 3, 8, 23, 26, 34, 39, 15.

These would be grouped:

0-9:        6
10-19:    3
20-29:    4 
30-39:    3

You can work out mean and variance and other statistics exactly for ungrouped data.

For grouped data you don't know the actual values so you can only estimate statistics from the data.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

EbenezerSon

Member

Registered: 2013-07-04

Posts: 554

Re: About Statistics

Than you Bundy - but wanted to quickly chip in this;
The average test mark for a class of 21 students is 65. Peter's mark was recorded as 35 instead of 55. What is the correct average mark for the test?
I had 62.8571 as answer, is that correct?

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I know only one thing - that is that I know nothing

Bob

Administrator

Registered: 2010-06-20

Posts: 10,619

Re: About Statistics

hi EbenezerSon

recorded as 35 instead of 55

So the total was 20 lower than it should have been.  The average should have gone up with the correct figure.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob