# Research question

Please identify a research question that can be addressed with a hypothesis test. An example might be to identify the presence of bacteria in a batch of milk.

Define your research question as a statement.

What is your measurement parameter?

What is the critical value?

Now express your research question as a null and an alternate hypothesis.

Define the meaning of a Type I error and a Type II error, the meaning in terms of the correctness of your response to the situation. My example might mean we sell milk that contains bacterial contamination and our customers get sick or we incur the huge cost of a recall.

Consider the risk posed by your research question. What level of significance should your choose? Justify your choice in terms of the probability of making a Type I error and the probability of making a Type II error.

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#### Solution Preview

Hypotheses and Significance

Please identify a research question that can be addressed with a hypothesis test. An example might be to identify the presence of bacteria in a batch of milk.

Define your research question as a statement.

(Example selected from faculty.uncfsu.edu/dwallace/lesson%2010.pdf)

Suppose some species of plants grows at 2.3 cm per week with a standard deviation of 0.3 ( M = 2.3 s = 0.3). Suppose we take a sample plant and genetically alter it to grow faster. The new plant grows at 3.2 cm per week (X = 3.2). Did the genetic alteration cause the plant to grow faster than the general population?

We set alpha = .05.

The research question is

Genetically altered plants grow faster than the general population.

What is your measurement parameter?

The measurement parameter is increase in length of plants.

What is the critical value?

Critical value is the value of

z (normal distribution , used when sample size is large) which depends on the level of significance a (alpha) chosen for testing the hypothesis

or t (student distribution , used when sample size is small ) which depends on the level of significance a ...

#### Solution Summary

A research question is identified that can be addressed with a hypothesis test. The research question is defined as a statement, the measurement parameter identified, the critical value calculated. The research question is expressed as a null and an alternate hypothesis.