Maths stats advice. easy 10 points. just little more info added?

You have to know whether a variable is discrete or continuous to select which distribution applies. The binominal distribution, for example, is a discrete distribution; the Poisson and normal distributions are continuous distributions. Dealing with a population is very different from dealing with a sample. With a population, you know exactly what every value in the population is, so you know the mean, the standard deviation, and the exact shape of the frequency distribution. When you take a sample, you need to know how precisely you have estimated, for example, the mean of the population; something called the central limit theorem comes into play. In fact, the central limit theorem comes into play all over the place when you're doing hypothesis testing. You have to know whether a scale is ratio, interval, ordinal, or purely nominal in order to decide what sort of tests are appropriate. It was quite confusing for me at first. It may be quite confusing for you. Stick with it, pay attention, and ask questions. There is nothing stupid about asking a question if you're asking it with the intent to learn something. And good luck.