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See Figure 1 for assistance with navigating through the menus. Press :y to open the Data menu. In this menu, enter a list of xvalues for one-variable statistics, a list of pairs, (x, F) for weighted, one-variable statistics, a list of numbers xfor one-variable statistics, or a list of pairs, (x, y) for two-variable statistics. To enter data, key in a number and press I. Press :z to analyze the data. If you attempt to open the Statistics (Stats) menu before entering data, you will be redirected to the Data menu. When opened, the Stats menu displays 2Varsfor two-variable statistics. Press I repeatedly to select the type of statistical operations desired, two-variable, (2Vars),one-variable, (1Var), or one-variable weighted (1Weight). After selecting the type of statistical operation you want, select a sub-menu by pressing < or >, and press I to open it. Once in a sub-menu, press < or > repeatedly to view the results. To return from the sub-menu to the Statistics menu, press :z. Note: in one-variable modes, there are no items for yand the Predictionssub-menu is not available. Pressing I with the Predictionssub-menu displayed opens a sub-menu, in which you can choose among six different types of regression lines. See Figure 1. To select a specific type of regression line in the Predictionssub-menu, press I to cycle through the options. Note: if you press =, the calculator automatically selects the curve that is the best fit for your data. Once you select a regression line, press < to see the regression line parameters and perform predictions. 61 Statistical Operations Table 10-1 The Statistics Menu Items Menu Item Nb Item Description Number of items. X Mean Average of X values. Y Mean Average of Y values. X Std. Dev Standard deviation for X: a measure of how dispersed the x data values are about the mean. Y Std. Dev Standard deviation for Y: a measure of how dispersed the y data values are about the mean. X Population Dev Population Standard deviation for X: a measure of how dispersed the X data values are about the mean, assuming the data constitutes a complete set of data. Y Population Dev Population Standard deviation for Y: a measure of how dispersed the y data values are about the mean, assuming the data constitutes a complete set of data. S.E.SamP.X Sample error for X: a measure of how dispersed the X data values are about the mean sample standard deviation, assuming the data is a sampling of a larger, more complete data set. S.E.SamP.Y Sample error for Y: a measure of how dispersed the Y data values are about the mean sample standard deviation, assuming the data is a sampling of a larger, more complete data set. Pred X Predicts X for a given hypothetical value of Y, based upon the model calculated to fit the data. Pred Y Predicts Y for a given hypothetical value of X, based upon the model calculated to fit the data. a The acoefficient for the chosen regression model, which is the slope for a linear model. b The bcoefficient for the chosen regression model, which is the y-intercept for a linear model. Correlation The correlation coefficient for the given (x, y) data. The correlation coefficient is a number in the range -1 through 1 that measures how closely the calculated line fits the data. Covariance A measure of how much two variables change in relation to one another. Sigma X The sum of the x values. 62 Statistical Operations Table 10-1 The Statistics Menu Items Menu Item Description Sigma Y The sum of the y values. Sigma X2 The sum of the squares of the x values. Sigma Y2 The sum of the squares for the y values. Sigma XY The sum of the products of the x and y values. Statistics Example Sales for the last five months are represented by the pairs of values shown below, with the month number as x, and the sales values as y. Enter these into the Data menu. Using the Statistics menu for Predictions, predict sales for month seven. What is the linear regression line? What is the sum of all the y values? See Tables 10-2 and 10-3. Table 10-2 Months and Sales Month Sales Values 1 150 2 165 3 160 4 175 5 170 Table 10-3 Statistics Example Keys Display Description Opens Data menu. :y Inputs values for X(1) and Y(1). 1I1 50I Inputs values for X(2) and Y(2). 2I1 65I Inputs values for X(3) and Y(3). 3I1 60I Inputs values for X(4) and Y(4). 4I1 75I 63 Statistical Operations Table 10-3 Statistics Example Keys Display Description Inputs values for X(5) and Y(5). 5I1 70I Opens Stats menu. :z Opens Descriptive sub-menu.