Social Statistics: Hypothesis

The difference between a sample and a population

Null and research hypotheses What is a good hypothesis

This week

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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

What is a hypothesis?

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$$$ Time

Sampling: Sample vs. population Sampling errors measure how well a

sample approximates the characteristics of a population.

Research and reality

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

Sampling

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1. State the hypothesis2. Set decision criteria3. Collect data and compute sample

statistic4. Make a decision (accept/reject)

The Steps of Hypothesis Testing

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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

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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

Null hypothesis ()

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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.

Research hypothesis ()

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

Nondirectional research hypothesis

YXH :

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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

Directional research hypothesis

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Null hypothesis Nondirectional research hypothesis

Directional 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.

Exercises

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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.

Good hypothesis

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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

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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.

Exercises

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