Module #4 LAB.pdf

Module #4 LAB Descriptive Stats for One Numeric Variable Materials: ✓ PC or Laptop with the following minimum requirements: Operating system: Windows 7 or higher Processor: Intel or AMD x86 processor running at 1GHz or higher Memory: 1GB RAM or more recommended Minimum free drive space: 800MB Super...

Module #4 LAB Descriptive Stats for One Numeric Variable Materials: ✓ PC or Laptop with the following minimum requirements: Operating system: Windows 7 or higher Processor: Intel or AMD x86 processor running at 1GHz or higher Memory: 1GB RAM or more recommended Minimum free drive space: 800MB Super VGA (800x600) or higher-resolution monitor ✓ IBM SPSS Statistics Software ✓ Writing Materials Procedure: The Descriptives option produces a set list of descriptive Descriptive Statistics in SPSS (Explore and Frequencies) statistics: Explore The Explore procedure produces detailed mean, confidence interval for the mean (default univariate statistics and graphs for numeric scale 95% CI), 5% trimmed mean, median, variance, variables for an entire sample, or for subsets of a standard deviation, minimum, maximum, range, sample. interquartile range (IQR), skewness, kurtosis, and It can also be used to assess the normality of a standard errors for the mean, skewness and numeric scale variable with special inferential kurtosis. statistics and detailed diagnostic plots. Note that you can't pick and choose which of these To run the Explore procedure, click Analyze > Descriptive descriptive statistics to view -- it's all of them or Statistics > Explore. none of them The M-estimators option produces alternatives to the mean and median. See this page on the official IBM guide for more information. The Outliers option prints the top five highest and lowest values, and what case they are associated with. (If you have specified a "Label cases by" variable, that variable will print instead of the case number.) The Percentiles option produces the 5th, 10th, 25th, 50th, 75th, 90th, and 95th percentiles of the data. E. Plots: Optional choices for which graphs to produce; this is also where the normality test options are. Plot choices include boxplots, stem-and-leaf plots, histograms, and normality plots. By default, the Explore procedure produces boxplots and stem-and-leaf plots for each continuous numeric variable. F. Options: A. Dependent List: Control how Missing Values should be treated. By The continuous numeric variables you wish to default, listwise exclusion is used. analyze. B. Factor List: (Optional) Categorical variables to subset the analysis by. The procedure will produce individual summaries of the numeric variable with respect to each category. C. Label Cases by: (Optional) An ID variable with "names" for each case. These names appear in reports of outliers. If not specified, SPSS will use the row number to label the case. D. Statistics: Optional choices for what statistics to report. Choices are Descriptives (enabled by default), Listwise exclusion M-estimators, Outliers, and Percentiles. will exclude from analysis any cases with missing values for any of the selected variables.  If listwise exclusion is selected, the number of valid cases for each variable will be the same. Pairwise exclusion will compute each variable's mean using all cases with nonmissing responses for that particular variable. If pairwise exclusion is selected, the number of valid cases for each variable may be different. Report values only affects analyses that include a factor variable. If this option is selected, cases with missing values for a factor variable will be treated as a distinct category. Using the Frequencies Procedure with Scale Variables To call the Frequencies procedure, click Analyze > Descriptive Statistics > Frequencies. Most of the statistics in the Central Tendency, Dispersion, and Distribution groups are valid for continuous variables; the only exception is the Mode, which very rarely has a useful interpretation for situations involving continuous variables. Most of these statistics are identical to the ones that can be obtained with Descriptives, Compare Means, or Explore, so they will not be covered again here. One noticeable exception to this is the Percentile Values group, which is unique to the Frequencies procedure: The Quartiles option produces the first, second, and third quartiles (i.e., the 25th, 50th, and 75th percentiles, respectively). The Cut points for n equal groups option will divide the dataset into n equally sized groups and report the percentiles. For example, if the user specifies n=5, then the output will report the 20th, 40th, 60th, and 80th percentiles. Or, if the user specifies n=10, then the output will report the 10th, 20th, 30th,..., 90th percentiles. The Percentiles option allows the user to specify the exact percentiles to report. The percentiles should be entered as A. Variable(s): whole numbers. The variables to analyze with the Frequencies You can select more than one option in the Percentile Values procedure. group. If your selections request overlapping information, To include a variable for analysis, double-click on that information will not be printed twice. its name to move it to the Variables box. C.Charts: Opens the Frequencies: Charts window, which You can add several variables to this box to obtain contains various graphical options. Options include bar statistics for each variable. charts, pie charts, and histograms. Histograms are the only B. Statistics: appropriate option for continuous variables; bar charts and Opens the Frequencies: Statistics window, which pie charts should never be used with continuous variables. If contains various descriptive statistics, most of requesting a histogram, the optional Show normal curve on which are suitable for continuous numeric histogram option will overlay a normal curve on top of your variables. histogram, which can be useful when assessing the normality of a variable. Note that the options in the Chart Values area apply only to bar charts. These buttons will be greyed out if the radio button for Histograms is selected. D. Format: Opens the Frequencies: Format window, which contains options for how to sort and organize the table output. The Order by options are not relevant to continuous variables, but the Multiple Variables options allow for customization of output when two or more continuous variables are specified. Compare variables places the descriptive statistics for the numeric variables side-by-side Organize output by variables creates separate summary tables for each numeric variables E. Display frequency tables: When checked, frequency tables will be printed. (This box is checked by default.) If this check box is not checked, no frequency tables will be produced, and the only output will come from supplementary options from Statistics or Charts. You will want to uncheck this box if using the Frequencies procedure on a continuous numeric variable. (If this box is left checked, a frequency table will be produced where each unique number is treated as its own category. This could lead to a table with 100+ categories, depending on the number of observations in your dataset.)