For each of the following situations, determine:

Question

a) the null and research hypotheses;
b) the hypothesis test used (normal curve, single sample t-test, dependent samples t-test, independent samples t-test, ANOVA). For situations 1, 3, 4, and 5, also state whether the test is unilateral or bilateral;
c) the degrees of freedom
d) the critical value (cutoff score on the comparison distribution);
e) your sample’s test score;
f) your conclusion on whether to accept or reject the null hypothesis (you must show how the comparison of your cutoff score with your sample’s test score leads to your conclusion).

For each situation, assume that any information that is not provided is therefore unknown to the researcher. Also, assume that the level of significance (alpha) is 0.05.

1. A researcher wants to determine whether alcohol increases the amount of motor coordination errors. She selects two samples of 25 participants each. One group receives 5 ounces of alcohol, while the other group receives 5 ounces of water. She then observes the amount of errors that the participants make in a labyrinth. The test statistic was 2.81.

2. The same researcher wants to study the effect of caffeine on memory. She selects four samples of 15 participants each. The groups receive 0, 2, 4, and 6 cups of coffee, respectively. The researcher takes note of the amount of words that the participants remember after studying them for 20 seconds. The test statistic was 3.15.