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 Statistics 2 Definition List A list of S2 definitions required for the Edexcel exam  Population – an entire set of individuals or items. Finite Population – a population where each individual member can be given a number. Infinite Population – a population where it is impossible to number each member. Statistic – a random variable that is a function of known observations from a sample involving no unknown parameters. Sampling Distribution – if all possible samples are taken, then the values of the statistics along with their associated probabilities will form a probability distribution called the sampling distribution. Sampling Frame – a list of all the members of the population. Sampling Unit – individual member or element of the population or sampling frame. Census – when every member of the population is investigated. Sample – a selection of items from the population that are used to represent the population. Critical Region – the range of values of the test statistic that would lead you to incorrectly reject H0. Level of Significance – the probability of incorrectly rejecting H0. Hypothesis – a statement concerning a population parameter. Hypothesis Test – A hypothesis test is a mathematical procedure to examine a value of a population parameter proposed by the null hypothesis H0 compared to the alternative hypothesis H1. Test statistic – In a hypothesis test the evidence comes from a sample which is summarised in the form of a test statistic. Critical Value – the boundary value of a critical region. One tailed test – looks for an increase or decrease in a parameter and has one single critical value. Two tailed test – looks for both an increase and a decrease in a parameter and has 2 critical values.  