Exam 10: Introduction to Hypothesis Testing: Using the Sign Test

A psychologist is interested in whether hypnosis affects brain dominance. Twelve college students from the freshmen class are randomly sampled for an experiment. The experiment has two conditions which are given on different days. In condition 1, the students are hypnotized and then given a test which measures the relative dominance of the right and left hemispheres. The higher the score, the more dominant is the right hemisphere. In condition 2, the same students are given the test again, only this time they are not hypnotized but are in their normal state of consciousness. The following scores are obtained. If you conclude to reject H ₀, the error(s) you may be making is(are) _________.

H₀ always asserts that the dependent variable has no effect on the independent variable.

If H 0 is false and we reject it, we have made a Type II error.

Define state of reality.

It is important to know the possible errors (Type I or Type II) we might make when rejecting or retaining H 0 _________.

Why do we directly evaluate H 0 rather than H 1 ? Explain.

Define one-tailed probability.

It is permissible to use a directional H 1 when there are good theoretical as well as strong supporting data to justify the predicted direction.

If you were a scientist who believes she has discovered an inexpensive new energy source that doesn't pollute, and you designed an experiment to assess whether or not this energy source actually worked, would you rather protect yourself from making a Type I or Type II error? Why?

It is appropriate to determine if H₁ is directional or nondirectional after the data is analyzed.

If we reject H₀ then we are absolutely certain the independent variable affected the dependent variable.

A pharmacologist recently developed a drug that, in theory, should have an effect on the activity of the lateral hypothalamus. It is likely that such a drug would have an effect on appetite. A small pilot experiment is designed to test this hypothesis.

If results are statistically significant, the independent variable must have had a large effect.

In an experiment involving a nondirectional alternative hypothesis, the obtained result was 7 pluses and 1 minus. To evaluate the null hypothesis, which of the following probabilities would you use?

Why is alpha usually set at 0.05 or 0.01?

Beta is the probability of retaining H₀ when H₀ is false.

Define reject null hypothesis.

It is impossible to get 20 pluses out of 20 pairs of scores in a replicated measures design due to chance alone.

If you reject the null hypothesis, you may be making _________.

Define Type I and Type II error. Why is it important to know the possible errors we might make when rejecting or retaining H 0 ?