In this essay, the different types of statistics used by psychology researchers will be explained and the key terms will be explained. Statistics is known as the science or practice of gathering and examining numerical data substantial amounts. It is known as the art of learning from data as stated by Ross (2010). There are two types of data; descriptive statistics and inferential statistics. Descriptive statistics make up the initial stage of statistical analysis and is a brief summary of the data that is collected. Inferential statistics follow descriptive statistics and deduce conclusions from the descriptive statistics available. Statistics makes use of quantitative or numerical data by analysing it. When data is collected from a large group of people, also known as the population, it includes every single person in that area. When collecting data is not practical, a sample is used instead. There are four main types of data, which include nominal scales, ordinal scales, interval scales and ratio scales. All of these different types of data are used in collecting and portraying statistics. Nominal scales are used when there are variables without any quantitative or numerical value. They are also known as labels. An example of this would be being either male or female. Ordinal scales show non-numeric concepts and the order of the numbers is important, but the difference between each number is not known or important. An example would be satisfaction from 1 to 5, with 1 being the least satisfied and 5 being the most satisfied. Interval scales use numbers to show the order as well as the difference between each number, however, do not have an absolute zero. An example of this would be a thermometer reading in Celsius. Ratio scales show the most information, the order, the difference between each value as well as show an absolute zero. An example of this would be a height and weight scale. The first type of statistics, descriptive statistics, summarises the group of data collected. The two ways in which data is summarised are central tendency and dispersion. The central tendency shows what the group of data is generally like and shows a common feature of the set of data. The three measurements of central tendency include mean, median and mode. The mean is the average of the data and is the most representative value. To calculate the mean or average, all the numbers are added together and then divided by the number of numbers being added. The median is the number in the middle of the data once it has been arranged in ascending order. The mode is the number that occurs the most frequently in a set of data. Dispersion, on the other hand, looks at the differences internally between the data. The variation in the data is known as the dispersion. Standard deviation is the most common method of measuring the dispersion. It is used alongside the mean to show how much the values differ from the mean value. There are various other methods used within descriptive statistics, including the range, interquartile range, statistical distribution, probability and normal distribution.