Aim: What is the P-value method for hypothesis testing? Quiz Friday

P-value Usually test hypotheses at the common alpha levels of 0.05 and 0.01 and sometimes 0.10 The choice of the alpha level depends on the seriousness of the type I error P-value (probability value): is the probability of getting a sample statistic (such as the mean) or a more extreme sample statistic in the direction of the alternative hypothesis when the null hypothesis is true – In other words, the P-value is the actual area under the standard normal distribution curve representing the probability of a particular sample statistic or a more extreme sample statistic occurring if the null hypothesis is true.

Procedure 1.State the hypothesis and identity the claims 2.Compute the test value 3.Find the P-value 4.Make the decision 5.Summarize the results

Example A researcher wishes to test the claim that the average age of lifeguards in Ocean City is greater than 24 years. She selects a sample of 36 guards and find the mean of the sample to be 24.7 years, with a standard deviation of 2 years. Is there evidence to support the claim at α = 0.05? Use the P-value method.

Example Solution Step 1: State the hypotheses and identify the claim Step 2: Compute the test value Step 3: Find the P-value (from z-table) – area under the curve Step 4: Make the decision – Since the P-value is less than 0.05, the decision is to rejected the null hypothesis Step 5: Summarize Results – There is enough evidence to support the claim that the average age of lifeguards in Ocean City is greater than 24 years.

Decision Rule When using a P-value If the P-value ≤ α, reject the null hypothesis If the P-value is > α, do not reject the null hypothesis