maths - working out the median?

[sphil]

So - Ds1 and I know that the median is the middle number. DS has been taught to order the numbers given and then work inwards, putting a finger on each outer number and moving in. But if you have the numbers 3,2,9,10,12,2 for example, do you count both twos?

If you do, we end up half way between 3 and 9. So is the answer 6? He is blithely writing 3.5, but that can't be right, surely?

If you only count one 2 the answer would be 9 -

You should include both 2s in the example you have given.

2,2,3,9,10,12

median is indeed 6 (half way between 3 and 9 or (3+9)/2 )

Ignore the frequency of the numbers, so a re-order becomes 2,3,9,10,12 with the median therefore being 9.

The frequency is used in calculating the mode average - in this example the mode (most common) is 2.

The mean average adds all numbers, 2+2+3+9+10+12 and divides by the number of numbers added (6).

Pickledsiblings is right.

You don't ignore the frequency of the numbers. If there were 1,1,3, 3,3,5,7 then your median would be 3.

So at the moment it's 3:1 for including both numbers...

Mean and mode are fine - got those ( though it involved quite a bit of pacing from DS)

Now range - that would be 10 in this example?

Yes include multiple occurances of the same number

what pickledsiblings said

range is 10

are you going to do quartiles and stuff as well?

You definitely include all numbers. Ignore the one dissenter!

Range is indeed 10, and for the median you DO include EVERY number, so it would be 6 (3+9)/2. Halfway through Y1 of a maths degree, so am certain!

hold on
as it happens I am doing a course on this at the mo and have a prog on the computer

Variable N N* Mean SE Mean StDev Minimum Q1 Median Q3 Maximum
C1 6 0 6.33 1.84 4.50 2.00 2.00 6.00 10.50 12.00

Variable N N* Mean SE Mean StDev Minimum Q1 Median Q3 Maximum
C1 6 0 6.33 1.84 4.50 2.00 2.00 6.00 10.50 12.00

Hmm that's not coming out very well

Anyway there you go

Quartiles?? what be they then? Do they do them in Year 6 SATS, cos if not we're not interested

I don't think so! I was just trying to show off

Sardinequeen - YOU are mean!

Another vote for counting both 2's

Thanks everyone - I am sure I'll be back in the next few weeks...

He'll prob be doing quartiles next week

Hey Diddle Diddle,
the median's the middle
you add and divide for the mean
the mode is the number that shows up the most
and the range is the difference between

Any more gems like that snowball? :o

Oooh I like that!

thats great - will help DS no end. He loves rhymes and mnemonics etc. Will tell his teacher too!

Fantastic snowball thank you for sharing that :O