Frequency Distributions & GraphsFrequency Distributions(cont.)Slide 4GraphsSlide 6Shapes of DistributionsA note on HW4SPSS -GraphsSPSS (cont.)Frequency Distributions & GraphsWed, Feb 11th, 2004Frequency DistributionsOrganize data into a table showing # observations in each categoryIncludes category, its frequency (f), and its proportion (P)–Proportion (P) = f / N (total sample size)Score f P10 32 .319 45 .438 27 .26Total 104(cont.)If too many categories, use grouped freq distribution (you decide the appropriate class interval)Exam Score f %90-100 12 34.3%80-89 15 42.9%70-79 8 22.8%Total 35 100%(cont.)May prefer Cumulative Distributions to show cumulative freq or prop/%:–Show f or p at or below each category (label cf or cp)–Add f or p for each category to total f or p for all previous categoriesScore f P cf cP10 32 .31 104 1.009 45 .43 72 .698 27 .26 27 .26Total 104GraphsBar chart – shows frequency of nominal/ordinal variables. –Indicates frequency or % on y axis, categories on x axis; bars do not touch–Example:Histogram – shows frequency of interval/ratio variables–Frequency or % on y axis, order values from low to high on x axis; bars touch–Example:(cont.)Frequency polygon – same as histogram, but instead of bars, use points at midpoint, connect w/lines–Time Series Chart is similar w/time on x axis–Examples:Shapes of DistributionsExamine histogram, bar graph, look at overall shape:–Bell-shaped distribution – most scores in middle; fewer at extremes–Positively skewed distribution: most scores at low end of scale, tail of distribution points to high (pos) end–Negatively skewed distribution: most scores at high end of scale, tail points to low (neg) end of scaleA note on HW4HW4 due Monday…Ch 2 # 1, 6, 10, 13 and SPSS problems 1a-1d (all parts of #1) and 3a & 3b at end of ch 2You’ll need the data “GSS98PFP-A” to do the SPSS hw problems–If you have the book CD-rom, it’s on there…if not, let me know now and I’ll email you the data file.SPSS -GraphsUse student.sav data in link in labUse menus at top:–For tables, use “Analyze  Descriptive Statistics  Frequencies”–Then indicate variables you want in table, hit “OK”–Switches to output window–Switch back to data view to do more analysesSPSS (cont.)For graphs, use menu “Graph”, then bar graph or histogramExamine shapes of these distributionsNOTE: skip “Stem & Leaf Plot” section of the lab and