1、Chapter 9INTRODUCTION TOHYPOTHESIS TESTINGStatistics for Business(ENV)1Hypothesis Testing9.1 Null and Alternative Hypotheses and Errors in Testing9.2 z Tests about a Population with known 9.3 t Tests about a Population with unknown 2Hypothesis testing-1Researchers usually collect data from a sample
2、and then use the sample data to help answer questions about the population. Hypothesis testing is an inferential statistical process that uses limited information from the sample data as to reach a general conclusion about the population.3 A hypothesis test is a formalized procedure that follows a s
3、tandard series of operations. In this way, researchers have a standardized method for evaluating the results of their research studies. 4Hypothesis testing-25The basic experimental situation for using hypothesis testing is presented here. It is assumed that the parameter is known for the population
4、before treatment. The purpose of the experimentis to determine whether or not the treatment has an effect. Is the population mean after treatment the same as or different from the mean before treatment? A sample is selected from the treated population to help answer this question.Procedures of hypot
5、hesis-testing61. First, we state a hypothesis about a population. Usually the hypothesis concerns the value of a population parameter. For example, we might hypothesize that the mean IQ for UIC students is = 110.2. Next, we obtain a random sample from the population. For example, we might select a r
6、andom sample of n = 100 UIC students.3. Finally, we compare the sample data with the hypothesis. If the data are consistent with the hypothesis, we will conclude that the hypothesis is reasonable. But if there is a big discrepancy between the data and the hypothesis, we will decide that the hypothes
7、is is wrong.Null and Alternative Hypotheses The null hypothesis, denoted H0, is a statement of the basic proposition being tested. It generally represents the status quo (a statement of “no effect” or “no difference”, or a statement of equality) and is not rejected unless there is convincing sample
8、evidence that it is false. The (scientific or) alternative hypothesis, denoted Ha (or H1) , is an alternative (to the null hypothesis) statement that will be accepted only if there is convincing sample evidence that it is true. These two hypotheses are mutually exclusive and exhaustive.78Determined by the level of significance or the alpha level9Alpha level of .05 - the probability of rejecting the null hypothesis when it is true is no more than 5%.Z10The locations of the critical region boundaries for three different levels of significance
