TAILIEUCHUNG - introduction to spss RESEARCH METHODS & STATISTICS HANDBOOK PHẦN 7

Mức độ dữ liệu Dữ liệu phù hợp với một trong bốn cấp độ: • Các • Các • Các • Các danh nghĩa (phân loại) - giá trị, hoặc là hiện nay hay không TT - giá trị được xếp hạng tương đối so với những người khác Interval - giá trị được ghi tuyệt đối cho những người khác Tỷ lệ giá trị được ghi tuyệt đối những người khác và một số không có ý nghĩa | must be extremely aware of issues such as the level of data used and characteristics of the population namely distributional assumptions. Levels of Data Data conforms to one of four levels Nominal categorical - the value is either present or not Ordinal - the value is ranked relative to others Interval - the value is scored absolute to others Ratio - the value is scored absolute to others and to a meaningful zero An example Consider three horses in a race. Coding the race times under a nominal level will tell us if any particular horse won the race or not . Guttman s Folly did not win . Coding under an ordinal level we can tell where a given horse came in relative to the others . Guttman s Folly came in second . Coding under an interval level we know where a given horse came absolute to the others . Guttman s Folly was seconds faster than Galloping Galton but seconds slower than Cattell s Chance . Coding under a ratio level we would know where a given horse came absolute to the others and a meaningful common zero point to all of them . Guttman s Folly came home in seconds Galloping Galton was seconds and Cattell s Chance was seconds . Sometimes we use dichotomies. This basically is a variable that can only take one of two values either present 1 or absent 0 . Its level therefore is nominal. Descriptive Statistics Measures of Central Tendency There are three measures that give an indication of the average value of a data set Mode - this is the most common value in the data set most appropriate for nominal level data Mean - this is the arithmetic average the one most familiar to people most appropriate for interval and ratio level data Median - this is the middle value in the data set most appropriate for ordinal level data As an example the following are the numbers of children for seven families 0 0 0 1 1 5 7 The mode most common value is 0. The mean is calculated as 14 sum of all seven scores divided by seven number of cases .

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