ABSTRACT
When data are obtained by counting and only whole numbers are possible, the data are called discrete. Measured data can have any value within certain limits and are called continuous (see Problem 1). A set is a group of data and an individual value within the set is called amember of the set. Thus, if the masses of five people are measured correct to the nearest 0.1kg and are found to be 53.1kg, 59.4kg, 62.1kg, 77.8kg and 64.4kg, then the set ofmasses in kilograms for these five people is:
{53.1,59.4,62.1,77.8,64.4} and one of the members of the set is 59.4 A set containing all the members is called a population. Some members selected at random from a population are called a sample. Thus all car registration numbers form a population, but the registration numbers of, say, 20 cars taken at random throughout the country are a sample drawn from that population. The number of times that the value of a member occurs in a set is called the frequency of that member. Thus in the set: {2,3,4,5,4,2,4,7,9}, member 4 has a frequency of three, member 2 has a frequency of two and
The relative frequency with which any member of a set occurs is given by the ratio:
frequency of member total frequency of all members
For the set: {2,3,5,4,7,5,6,2,8}, the relative frequency of member 5 is 29 Often, relative frequency is expressed as a percentage and the percentage relative frequency is: (relative frequency×100)%.
