Basic Statistics

1. Variable - is a symbol that stands for a value that may vary; the term usually occurs in

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opposition to constant, which is a symbol for a non-varying value, i.e. completely fixed or fixed in the context of use. Quantitative Variable – Variables that have are measured on a numeric or quantitative scale. Ordinal, interval and ratio scales are quantitative. Qualitative variable – are variables with no natural sense of ordering. They are therefore measured on a nominal scale. Discrete Variable – is one that cannot take on all values within the limits of the variable. For example, responses to a five-point rating scale can only take on the values 1, 2, 3, 4, and 5. The variable cannot have the value 1.7. A variable such as a person's height can take on any value. Continuous Variable – is one for which, within the limits the variable ranges, any value is possible. is one for which, within the limits the variable ranges, any value is possible. For example, the variable "Time to solve an anagram problem" is continuous since it could take 2 minutes, 2.13 minutes etc. to finish a problem.

What are the scale of measurements? - is the assignment of numbers to objects or events in a systematic fashion. a. Nominal measurement consists of assigning items to groups or categories. No

quantitative information is conveyed and no ordering of the items is implied. Nominal scales are therefore qualitative rather than quantitative. b. Ordinal scales are ordered in the sense that higher numbers represent higher values. c. Interval measurement scales one unit on the scale represents the same magnitude on the trait or characteristic being measured across the whole range of the scale. d. Ratio scales are like interval scales except they have true zero points. A good example is the Kelvin scale of temperature. This scale has an absolute zero. Thus, a temperature of 300 Kelvin is twice as high as a temperature of 150 Kelvin. What are the ways of presenting data? Graphs - where, for instance, sales values could be plotted against months. Histograms - which look like towers of square buildings and are used to represent the proportions of differing items e.g. sales of different commodities. Pie charts - which are circles with different sections showing proportions , as with histograms Spread sheets - on which sales or purchase or usage of differing commodities can be shown against dates, months, years, and analysed in almost any way you want. Bar charts - which show progress of work in different areas. Critical path networks - which show how different operations interact with each other. Simple tables - This can show all sorts of relationships. What are the types of graphs?

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(1) stem and leaf displays, (2) histograms, (3) frequency polygons, (4) dot plots, (5) box plots, and (6) scatterplots.