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Review Descriptive Statistics - Advanced Tab

Select the Advanced tab of the Review Descriptive Statistics dialog to access options to review descriptive statistics and graphs of the data. To quickly review the most common descriptive statistics, use the Quick tab of the Review Descriptive Statistics dialog. Additional options are also available on the Matrix tab.

Means & standard deviations. Click the Means & standard deviations button to display a spreadsheet with means and standard deviations. The mean of the sample is an unbiased estimate of the population mean. By default the standard deviation is computed as the square root of the sum of squared deviations about the mean (SS) divided by N - 1 (an unbiased estimate of sigma2). The resulting statistic is an estimate of the population sigma (this statistic can then be used to draw inferences about the population from which the sample was drawn). You can use the SD = Sqrt(Sums of Squares/N) check box (see below) to compute the standard deviation as the SS divided by N. This resultant statistic is a description of the standard deviation in this sample (no inferences should be drawn from this statistic, about the population that the sample came from).

A particularly useful Graph of Input Data for this spreadsheet is a histogram (frequency distribution) of the chosen variable, with the normal distribution superimposed. This plot can be very useful as a quick check of whether the assumption of normality has been violated by the respective variable.

Correlations. Click the Correlations button to display a correlation matrix spreadsheet of the selected Variables. A particularly useful Graph of Input Data for this spreadsheet is a scatterplot of the respective two variables. The plot will indicate the regression line as well as the 95% confidence limits for the regression line.

Covariances. Click the Covariances button to display a spreadsheet with covariances. A particularly useful Graph of Input Data for this spreadsheet is a scatterplot of the respective two variables. The plot will indicate the regression line as well as the 95% confidence limits for the regression line.

Box & whisker plot. Click the Box & whisker plot button to display the standard variable selection dialog, which allows you to choose the variables you wish to plot in a box and whisker plot. After you have selected the variables, the Box-Whisker Type dialog, which allows you to choose the type of box and whisker plot (showing medians and quartiles, or  means and standard deviations, etc.), will be displayed. Finally, the specified box and whisker plot will be displayed.   

Matrix plot of correlations. Click the Matrix plot of correlations button to display the standard variable selection dialog, which allows you to choose the variables you wish to plot in a matrix scatterplot. Next, the matrix scatterplot for the selected variables selected will be displayed.

SD = Sqrt(SS/N). Select the SD = Sqrt(SS/N) check box to compute the standard deviation as the square root of the sum of squared deviations about the mean (SS) divided by N. In other words, the SD = Sqrt(SS/N) check box affects the way in which the standard deviations (option Means & standard deviations, above) and variances-/covariances (option Covariances, above) are computed. If this check box is selected, the resultant statistics are descriptions of the standard deviation, variance, and covariance in this sample (no inferences should be drawn from this statistic, about the population that the sample came from). The setting of this switch only affects the respective values in the spreadsheets; it does not affect any subsequent computations.