UASTAT151Ch2 - 2.1 Types of Data Defn A variable is any characteristic that is recorded for subjects in a study Qualitative(categorical cannot

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2.1 Types of Data Def’n: A variable is any characteristic that is recorded for subjects in a study. - Qualitative (categorical): cannot assume a numerical value but classifiable into 2 or more non-numeric categories. e.g. gender, smell - Quantitative (numerical): measured numerically. - Discrete: only certain values with no intermediate values. e.g. integers, grades - Continuous: any numerical value over a certain interval or intervals. e.g. GPA, gas prices Def’n: A frequency table (for qualitative data) is a listing of possible values for a variable, together with the # of observations for each value. Major Frequency ( f ) Relative frequency Percentage (%) Science Arts Business Nursing Other = f frequency frequency Relative _ pctg. = (Relative frequency) x 100 2.2 Graphical Summaries Def’n: A pie chart is a circle divided into portions that represent relative frequency belonging to different categories. e.g. (above table used in class) Look for : categories that form large and small proportions of the data set. A bar graph displays vertical bars whose heights represent the frequencies of respective categories. e.g. (above table used in class) Look for : frequently and infrequently occurring categories. Graphs for quantitative variables: Def’n: A stem-and-leaf plot has each value divided into two portions: a stem and a leaf. The leaves for each stem are shown separately in a display. (Values should be ranked.) Look for : - typical values and corresponding spread - gaps in the data or outliers - presence of symmetry in the distribution - number and location of peaks Ex2.1) U.S. Box Office for weekend of January 2, 2011 25.8 24.4 18.8 12.4 10.3 10.0 9.8 9.3 8.9 7.8 0 | 7.8 8.9 9.3 9.8 1 | 0.0 0.3 2.4 8.8 2 | 4.4 5.8
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A comparative S-and-L plot has a common stem to compare two related distributions: 9.8 8.4 7.3 7.0 6.8 5.2 4.8 | 0 | 7.8 8.9 9.3 9.8 5.0 3.8 0.7 | 1 | 0.0 0.3 2.4 8.8 | 2 | 4.4 5.8 Note: Dot plots also exist (see p. 33 in textbook), but “replace” the values with dots. Def’n: A histogram , like a bar graph, graphically shows a frequency distribution. The data here, however, is quantitative. Look for : - central or typical value and corresponding spread - gaps in the data or outliers - presence of symmetry in the distribution - number and location of peaks The data divide into intervals (normally of equal width).
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This note was uploaded on 07/31/2011 for the course STAT 151 taught by Professor Henrykkolacz during the Winter '07 term at University of Alberta.

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UASTAT151Ch2 - 2.1 Types of Data Defn A variable is any characteristic that is recorded for subjects in a study Qualitative(categorical cannot

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