Social Statistics: Hypothesis

This week The difference between a sample and a population Null and research hypotheses What is a good hypothesis

What is a hypothesis? Hypothesis Research questions  hypothesis An educated guess Research questions  hypothesis A good hypothesis translates a problem or research question into a form that is more amendable to testing Practical way: test your hypothesis in a sample and generalize it to the larger population

Research and reality $$$ Time Sampling: Sample vs. population Sampling errors measure how well a sample approximates the characteristics of a population.

Sampling A representative sample Represent population as close as it can Ensuring the high similarity of both Time and $$$

The Steps of Hypothesis Testing State the hypothesis Set decision criteria Collect data and compute sample statistic Make a decision (accept/reject)

Null hypothesis Assumes no relationship between two variables that you are going to study Such as there will be no difference in the average score of 9th graders and the average score of 12th graders on the ABC memory test. There is no difference between white and black families in the amount of assistance offered to their children in school-related activities.

Null hypothesis ( 𝐻 0 ) A starting point In the absence of any other information  guess? Benchmark against other outcomes To compare with other observed outcomes to see if these differences are due to some other factors

Research hypothesis ( 𝐻 1 ) A definite statement that there is a relationship between variables Null hypothesis  research hypothesis There is no difference between white and black families in the amount of assistance offered to their children in school-related activities. There is a difference between white and black families in the amount of assistance offered to their children in school-related activities.

Nondirectional research hypothesis Reflects the difference between groups, but the direction of the difference is not specified (such as more than or less than)

Directional research hypothesis Reflects the difference between groups, and the direction of the difference is specified. The average score of 12th graders is greater than the average score of 9th graders on the ABC memory test. Either H: X > Y or H: X < Y

Exercises Null hypothesis Nondirectional research hypothesis There is no difference between the score of the test and the time spending for assignments in the class. There is no difference between the consumption of ices cream and crime. There is no difference between reading more papers and writing good paper. There is no differences for the kid’s reading behavior and kid’s eating habit.

Good hypothesis Criteria Stated in a declarative form and not as a question Posits an expected relationship between variables Reflects theory or literature Be brief and to the point Testable and measureable Parents who enroll their children in after-school programs will miss fewer days of work in one year and will have a more positive attitude toward work than will parents who do not enroll their children in such programs.

Exercises It is know that, nationally, doctors working for health maintenance organizations (HMOs) average 13.5 years of experience in their specialties, with a standard deviation of 7.6 years. The executive director of an HMO in a Western state is interested in determining whether or not its doctors have less experience than the national average. A random sample of 150 doctors from HMOs shows a mean of only 10.9 years of experience. Please state both the research and the null hypotheses for above situation.

Exercises Take two empirical research articles, find What is the null hypothesis What is the research hypothesis Create your own null and research hypothesis in your interested area. Evaluate your hypothesis based on the criteria, What are hypotheses for your group project? Please write a paragraph to summarize.