What is meant by distribution?

Question

I was reading Biostatistical Analysis By Zar and stumbled upon the following:

Chi square goodness of fit is frequently desired to obtain a sample of nominal scale data to infer whether the population from which it came conforms to a specialised theoretical distribution.

I came across this term quite a number of times in a video of the same by Khan academy.

I tried to google it up but wikipedia is not very comprehensible to me.

So what does it mean? Explaining it in a very simple way will be much appreciated.

P.S. I had Mathematics till class X.

Answer 1

The topic is probability distribution.

This expression denotes a function that associates the values taken by a random variable (some unpredictable event that you somehow rate) and a probability that this value is achieved.

For example, the number of tails in a triple drawing of a fair coin gives the distribution

$$ 0\to\frac18\\ 1\to\frac38\\ 2\to\frac38\\ 3\to\frac18,$$

meaning that in the long run, you will get one eighth of the drawings with no tail, three eighths with a single tail and so on.

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The Chi-square test which you mention is a statistical technique used to determine if a given random variable indeed follows an hypothesized distribution. For example, it can tell you if a coin behaves like a fair one. (Technically, this is called a Binomial distribution.)