*Originally posted by bikingviking*

**[b]Grampy Bobby: 🙁
**

I assume you simply did not think of this, an accident. I simply can't beleve that you not by chance but by will, intetionally, posted a youtube link. Huh? No purely accidental for sure.

DO NOT BE LAZY AND just assume we want to spend our precious time with hearing (a bad youtube video, I DON'T ANYMORE watch them myfelf. BY PRI ...[text shortened]... and. I don't think anyone else is going to do this for you so do it yourself.

Please? 🙁[/b]

**Statistics: A Poem**
This poem is for all you guys

Who have some data that you need to analyze.

Listen closely, cause my rhymin' will show

All the IB statistics that you need to know

First step: gather up those data observations

Take the average, that's the mean, then standard deviation.

The mean is a measure of location,

The center of a population.

Unless you want to be a comedian,

Don't confuse it with the median.

Of course, the median's not much of a riddle

It's simply the number in the middle.

So just stick to the mean and you won't get confused,

It's the best measure of central tendency the statisticians use.

You could compute the mean in your slumber.

Just sum the scores and divide by the number.

Normally, the measures near the mean are many.

And in the tails, there's hardly any.

Now, in your measurements the scatter

Is something that really matters.

Cause it tells how close to the mean you're likely to be,

If a single measurement is all you can see.

Or if it will take a lot of measurements to be able

To get a mean value that's stable.

To calculate a data set's variation,

First find the mean and then each score's deviation.

Each deviation then you square,

And sum them up, all values share.

Divide the sum by N minus one.

Take the square root, and then you're done.

The standard deviation, called SD,

Is a good gauge of a trait's variability.

So when showing your data in a graphical plot,

The mean is usually drawn as a single black dot,

And with the dots there usually are,

Standard deviations shown as error bars.

Forget this number and face some IB hate,

Plus or minus one SD includes a percent of 68.

So we've discussed two moments of a distribution,

Calculated with each measurement's contribution.

But there's another part of statistics that is totally the best,

It helps you compare two sets of data — the t-test.

The t-test tells whether a difference you see

Reflects random scatter or reality.

Compute the t statistic and you can tell at a glance

Whether the result you found was likely due to chance.

T-testing is tough, but I'll help you survive:

First choose a confidence interval, usually point zero five.

But before you'll be able

To use the statistical table

You'll need to also know

The degrees of freedom. Oh No!

To get degrees of freedom, here's what you do,

It's the number of samples minus two.

When the measurements are paired, it's even more fun

It's simply the number of pairs minus one.

You can even compute t by hand if you dare

Just calculate the difference for each pair

The mean over SD is where you begin,

Then divide the result by the square root of N.

Now compare to the t-table, it's no big deal

To tell if your difference is by chance or real.

Or if the value you place on your time is greater,

Skip these instructions and use a calculator.

Your lab partners will think you're incredibly intelligent

If you're able to tell if your data is significant.

Prove your result is significantly different from zero

And you're sure to be a hero.

But watch out for one thing, a danger of sorts,

From a value that computers often report

They often provide when a t-test is done

The coefficient of correlation.

This is great to know since it tells you whether

Two things you measure tend to line up together.

But there are terrible IB threats

For any student who ever forgets

That even strong correlation

Can never imply causation.

(Published on May 29, 2012. An outline of IB statistics including mean,

standard deviation, t-test, and causation vs. correlation.)

**Note:** Hi, bikingviking. I've got Viking Ancestral roots too. Thanks for your request. Clarifications:

*Laziness* isn't now nor has ever been one of my shortcomings. A strong Swedish/New England Work Ethic has characterized my daily regimens since a long 12-month paper route on bicycle (snow shoes in winter) as a nine year old boy.

*Length of the poem* was the reason for suggesting a few minutes listen to an excellent quality and delightful reading by the Poet, Rachel Croxton. Judgmental on your part to dismiss it as "a bad youtube video" on the basis of your previous bad experiences. Kind regards, Bob