The basic goal of a statistical research project is to make a conclusion on the effect of changes of an independent variable on a dependent variable. There are two major types of statistical studies, experimental studies and post facto or after the fact studies. In both of these types of studies, the effect of changes of an independent variable on the behavior of the dependent variable are observed. The difference between the two is in how the study is actually conducted.
An experimental study involves taking measurements of the system under study, manipulating the system, and then taking additional measurements using the same procedure to determine if the manipulation may have modified the values of the measurements. A post-facto study involves reviewing existing data and making a determination about a correlation between two measurements.
There are four types of measurements or measurement scales used in statistics. The four types or level of measurement have different degrees of usefulness in statistical research. Typically, the most appropriate level of measurement is ratio measurement since ratio measurement provides the greatest flexibility in statistical methods that can be used for analysing the data. Interval measurement, such as IQ measurements or temperature measurements in degrees Celsius, is also used in statistical research.
The basic steps for any statistical research involves
1. plan the research including determining information sources, research subject selection, and ethical considerations for the proposed research and method,
2. design the experiment concentrating on the system model and the interaction of independent and dependent variables,
3. summarize a collection of observations to feature their commonality by suppressing details (descriptive statistics),
4. reach consensus about what the observations tell us about the world we observe (statistical inference),
5. document the results of the study.
Probability
The probability of an event is often defined as a number between one and zero. In reality however there is virtually nothing that has a probability of 1 or 0. You could say that the sun will certainly rise in the morning, but what if an extremely unlikely event destroys the sun? What if there is a nuclear war and the sky is covered in ash and smoke?
We often round the probability of such things up or down because they are so likely or unlikely to occur, that it's easier to recognize them as a probability of one or zero.
via [ DataBlog ]
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