Oh b****r!

THURSDAY 3 APRIL

AVERAGES
Having read your comments on yesterday’s blog, Kev, I’m fascinated by your definitions of the various kinds of averages. However....er.....I’m not quite with you. Would you mind illustrating with a concrete example......

The ages of a random group of 20 people (say, a group of truckshunters) are as follows: 18, 18, 19, 22, 22, 29, 30, 32, 36, 36, 45, 46, 46, 47, 59, 60, 61, 78, 93, 95.

What’s their ‘mean’ average age? And their ‘median’ average age? And their ‘modal’ average age? And how did you work the averages out?

MARGARET AND JIM
Once upon a time there lived in Newbiggin-by-the-Sea a lady called Margaret. In fact, she lives there still, happily and avidly listening to BBC Radio Newcastle. She passes her days listening to the provocative Mike Parr, the chirpy Jonathan Miles, the cheeky Alfie Joey....and her nights snoozing to the soporific Ian Robinson.

One morning, though - when Mike Parr was being paricularly provocative and naughty - she got up from her chair to make herself a cup of Earl Grey. Just then, something very strange happened. She looked out of her kitchen window at the very moment when Uncle Jim Bacon, the trusty BBC weatherman, was announcing the times of the high tide at Shields Bar. And, because Margaret had never lost her sense of curiosity, she began to wonder....

If the moon’s gravity affects the ebb and flow of something as bulky as the sea, why doesn’t it affect something as flimsy and insubstantial as clouds? Why aren’t clouds drawn towards the moon? After all, she reasoned, they are already closer to it than the sea is and the moon is usually in the sky, even during the day when you can’t actually see it.

She couldn’t get the enigma out of her head. Eventually, she came up with a way of resolving the puzzle. ‘I know!’ she exclaimed to Montmorency, her cat. ‘I’ll ask that nice, soporific Ian Robinson to have a word with Uncle Jim Bacon. He’s sure to know the answer!’

So she did. And I did. And he does.

Just in case any of you missed it, Uncle Jim - who obviously has several strings to his meteorological bow - followed up his on-air explanation with an email, which I reproduce below.

‘What I was trying to say without using the maths is that the force of gravity G = f ( m1xm2 ) / R squared

m1 and m2 are the masses of the two objects

f is a constant (doesn't count in this argument, its the same for both)

R is the distance between the two bodies (same for both)

Say m1 is the moon, R is the distance from moon to earth ( assume same for sea and cloud stuff )

m2 is the only thing that is different between the two examples. m2 is the mass of the ocean compared to the mass of a cloud droplet so the force of gravity between the moon and the ocean is many orders of magnitude greater than the force between the moon and a tiny cloud droplet. Infact the other forces on the cloud droplet are much greater, buoyancy and wind etc

Don't you just love physics......I'll take my anorak off now!

Jim'

So now you know. Don’t you?

CONTACT ME
Post comments on this blog or contact me in any one (or more) of these ways....
ian.robinson@bbc.co.uk
ianstuartrobinson@googlemail.com
text 07786 200954 (up to 0600, Monday to Friday)
call (between about 0545 and 0630 Monday to Friday) 0191 232 6565
Ian Robinson, The Nightshift, BBC Radio Newcastle, Spital Tongues, Newcastle-upon-Tyne NE99 1RN

NOTE
Please bear in mind that the views expressed in this blog are my own and NOT the views of the BBC.

6 comments:

gilly said...

hiya lan..i found the post very interesting..

the pic? speechless..
i,m wondering is that a missile..?
just hope the factories nowhere near me..

the averages ?
mind boggling..dare anyone stand up and admit like me they can,t get their head around them..

the pull of the moon..
its lunar effects..
studies have been done ...
psychiatric hospitals have more admissions at the time of the full moon than any other time of the month,
hence the word "lunacy"
lunatic asylum.

Im a closet cloud spotter..
cloud names and meanings..
stratus..meaning layer..

cirrus .. wispy or curly..

cumulus ...lump or heap.

add to this nimbus..means pouring down..
therefore..cumulus-nimbus ?
big lumpy clouds that pour down.
happens often here.

all this madness brought on by ians metion of surfing the net...

awesome..i,m guilty of using it too...
it just sums up something good in one word..
bye..

pickler AKA G8XGS said...

HI Ian
fork lift went an inch too far i guess.

Yes Jim Bacon is a clever guy apart from general physics he,s the best for telling you (me and other radio hams) about "tropo"
thats caused by temperature inversion it "enhances" radio propagation at vhf and above but to varying degrees.

his radio Amateur callsign is G3YLA.


Gilly i am struck dumb with the knowledge you have about the heavenly bodies"clouds"

gilly said...

hiya pickler ditto,
i,m struck dumb with your knowledge of ...
well, all things "radio"..
amazing.

Kev said...

I hope this helps:

The data is
18, 18, 19, 22, 22, 29, 30, 32, 36, 36, 45, 46, 46, 47, 59, 60, 61, 78, 93, 95

The arithmetic mean is the total of the 20 numbers divided by 20.
So the arithmetic mean = (18 + 18 + …. + 95)/20 = 892/20 = 44.6 years

The mode is the commonest item. There is not necessarily a single value for the Mode as is the case here. The odes are 18, 22, 36 and 46 as these values occur twice while the rest only occur once.

The median is the middle value when the data is listed smallest to largest or vice versa.
If there was an odd number of data items, say 7, the median is the 4th item with 3 values being smaller and 3 larger. ie ***|*|***
If there is an even number of items the median is not an actual value from the list as an even number of items splits exactly into two equal parts and does not leave a middle value. ie ****|****
To get round this problem the median is the value that is halfway between the middle two items. In Ian’s example this is
18, 18, 19, 22, 22, 29, 30, 32, 36, 36 | 45, 46, 46, 47, 59, 60, 61, 78, 93, 95
The median is halfway between 36 and 45 so it is 40.5

Sid said...

Morning folks. Been very busy trying to catch a mouse that's been eating me pease in the polytunnel.
Kev...I was just about to put that to paper. (what a fibber).

Hildie said...

Just dropping by to say hello - and that will just leave Maureen and Loz on the missing list! Hope you are all well. I've been to school today, teaching Reception Class, we weren't doing averages, mind you! A little boy named Taylor was talking to me about his Mammy. I said , "I know your Mammy, her name is Kerry, isn't it?" "Yes, it is, she's told me she knows you as well", he answered.
"But", I continued, "What's your Daddy's name?"
Giving me a condescending look, and speaking in a very distainful tone he replied, "DADDY!"
Ah, well, that'll teach me not to be nosy, won't it?