Degrees of Freedom denotes the number of samples that a statistician has the freedom to choose. Degrees of Freedom is based on a concept that one could not have exercised his /her freedom to select all the samples.
The concept can be explained by an analogy:
X+Y = 10 (1)
In the above equation you have freedom to choose a value for X or Y but not both because when you choose one, the other is fixed. If you choose 8 for X, then Y has to be 2. So the degree of freedom here is 1.
X+Y+Z = 15 (2)
In the formula (2), one can choose values for...
Web Analytics Terms
A
Abandonment: is the measure when a visitor exits or leaves a conversion process on a website and does not return later during the session.
A/B Testing: A method of banner ads, emails and landing pages testing by which a baseline control sample is compared to a variety of single-variable test samples.
Accuracy: The ability of a measurement to match the actual value of the quantity being measured. Accuracy is the foundation upon which your web analytics should be built. If you can't trust that your data is accurate, you can't make...
Statistics Formulas
Notation
Capitalization
In general, capital letters refer to population attributes (i.e., parameters); and lower-case letters refer to sample attributes (i.e., statistics). For example,
- P refers to a population proportion; and p, to a sample proportion.
- X refers to a set of population elements; and x, to a set of sample elements.
- N refers to population size; and n, to sample size.
Greek vs. Roman Letters
Like capital letters, Greek letters refer to population attributes. Their sample counterparts, however, are usually Roman letters. For...
Use of Statistical Analysis?
One sample t-test
One sample t-test, tests whether a sample mean significantly differs from a hypothesized value
One sample median test
One sample median test is used to test whether a sample median differs significantly from a hypothesized value.
Binomial test
Binomial test is used to test whether the proportion of successes on a two-level categorical dependent variable significantly differs from a hypothesized value.
Chi-square goodness of fit
A chi-square goodness of fit test is used to test whether...
Results of Statistical Analysis
Results of statistical analyses can indicate the precision of the results, give further description of the data or demonstrate the statistical significance of comparisons. Where statistical significance is referred to in text, the reference should be included in such a way as to minimize disruption to the flow of the text. Significance probabilities can either be presented by reference to conventional levels, e.g. (P < 0.05) or, more informatively, by stating the exact probability, e.g. (P = 0.023). An alternative to including a large...
Statistical Averages
Summary Statistics
After the data have been properly checked for its quality, the first and foremost analysis is usually for the descriptive statistics. The general aim is to summarize the data, iron out any peculiarities and perhaps get ideas for a more sophisticated analysis. The data summary may help to suggest a suitable model which in turn suggests an appropriate inferential procedure. The first phase of the analysis will be described as the...