HP 40gs HP 39gs_40gs_Mastering The Graphing Calculator_English_E_F2224-90010.p - Page 141

THE INFERENCE APLET This aplet is a very flexible tool for users investigating inference problems. It provides critical values for hypothesis testing and confidence intervals, and does this not only quickly but in a visually helpful format. It will be assumed in the explanations that follow that the reader is familiar with the concepts of hypothesis testing. In the Inference aplet the SYMB view is used to choose the test to be applied. 22 The NUM SETUP view is used to enter the information required to apply the test. These results can either be entered by hand or imported from the Statistics aplet using the button. The results are displayed either numerically in the NUM view or graphically in the PLOT view. Generally the information that is required for the NUM SETUP view is obtained by importing it from the Statistics aplet. The logic is that there is little point in including facilities in the Inference aplet that are already more than ably supplied in the Statistics aplet. Hypothesis test: T-Test 1-µ A company makes boxes of matches which are supposed to contain an average of 50 matches. A student has counted the contents of 20 boxes and found the results below. Using a 5% confidence level, decide whether the claim is correct. 47, 50, 52, 51, 53, 51, 49, 49, 52, 53, 54, 48, 53, 55, 52, 54, 54, 53, 48, 48 Enter the data into the Statistics aplet then change to the Inference aplet. Choose the test and the alternate hypothesis in the SYMB view of the Inference aplet. In this case we are working with a single sample and we do not know the standard deviation of the underlying population, so we will use the Student-t test and the alternate hypothesis that the mean of the real underlying population from which the sample was drawn is not equal to that of the proposed underlying population. 141