Hypothesis Testing 2011, 10, 25

Objectives Review distribution of sample means Descriptive statistics vs. inferential statistics Research hypothesis* Statistical hypothesis testing – One sample z test**

Population For IQ Score = sample mean; n=75 Distribution of Sample Means Probability Means

Descriptive statistics vs. inferential statistics procedures that help us organize and describe data collected from either a a sample or a population Inferential Statistics: The logic and procedures concerned with making predictions of inferences about the population from observations and analyses of a sample

Research Hypothesis Law & Order Not Guilty Guilty Reject it! Mutually Exclusive Supported

Research Hypothesis (Two-Tailed Test) The police department of a major city reports that the mean number of auto thefts per neighborhood per year is () 6.88 with a standard deviation () of 1.19. As the mayor of a suburban community just outside the major city, you’re curious as to how the auto theft rate in your community compares.  = 6.88   6.88 Reject it! Mutually Exclusive Supported

Research Hypothesis (One-Tailed Test) Information collected at a local university indicates that students are working on average () 15.2 hours per week while in school with a standard deviation () of 3.5 hours. A research suspects that fraternity members work less than the school average. Information collected from a random sample of 30 fraternity members, reveals a mean of 13.9 hours per week.   15.2  < 15.2 Reject it! Mutually Exclusive Supported

Probability Population For College Students’ = sample mean Working Hours = sample mean n = 30 Probability

One-Sample z-Test Step 1: State hypotheses Step 2: Set your decision criteria Step 3: Compute mean and Std. Err. Step 4: Compute the zobs score (test statistic)

One-Sample z-Test Step 5: Make a decision about your null hypothesis

Lecture Recap: Hypothesis Testing Review distribution of sample means Descriptive statistics vs. inferential statistics Research hypothesis* Without direction: Two-tailed test With direction: One-tailed test One sample z test** Five steps