Name Date PSYC 3402 HW Assignment 9 t-tests Directions: Write the null and alternate hypothesis, determine the appropriate ttest for each of the following problems, decide upon a decision rule, draw the rejection region, and write a statement that describes the relationship the researcher is entitled to make. (You may use Excel to calculate means, variance and standard deviation). 1. An investigator predicts that individuals that t the Type A Behavior Pattern (highly competitive and time conscious) will have higher scores on a questionnaire measure of need for achievement that individuals that t the Type B Behavior pattern (absence of Type qualities). The investigator collects need for achievement scores from 10 Type A subjects and 10 Type B subjects. Higher scores reflect greater levels of need for achievement. Type A Type B 12 8 10 10 8 11 15 12 9 16- 11 8 t'OOH-JJLUIOOHJUI 0 2. An investigator believes that families in Virginia have more children on average than the average number of children in the population of the United States. From census data the investigator knows that the mean number of children in the U.S. is 2.1 children. She draws a sample of seven families from the state of Virginia and obtains the number of children for each family. The data from this sample are presented below. Write the null and alternative hypotheses for testing the investigator's prediction. Scores for the seven families: 3, 6, 2, 0, 4, 6, 7 3. An investigator conducts a study to examine the benets of psychotherapy for individuals with depression. Specically, the investigator predicts that depressed individuals who receive psychotherapy in addition to drug therapy for depression will display significantly lower levels of depression than persons with a diagnosis of depression who receive only drug therapy. The investigator assigns 10 subjects to each of the two groups stated above. Aer three months the investigator measures depression using a scale in which higher scores reect higher levels of depression. Psychotherapy plus drug therapy group: 23, 19, 16, 18, 15, 22, 16, 18, 19, 20 Drug therapy only: 24, 2?, 26, 28, 2'9, 24, 26, 25, 22, 28 4. The mean productivity rating for all employees at a company was 3.8 on a ve point scale last year. This year you get ratings from a representative sample of een employees from the Human Research Management. Do the data from this sample provide evidence that employee productivity in the department of Human Resource Management is significantly higher than in the company as a whole? Scores: 4.1, 3.9, 3.5, 4.0, 4.4, 4.3, 4.2, 4.5, 3.9, 3.6, 4.2, 4.4, 4.1, 4.3, 4.2 5. An investigator believes that young adults have better accuracy recognizing young adults than children. The investigator conducts a study on 19 young adults by showing them a series of photographs and later testing their recognition accuracy. Below are the accuracies for each participant for both the children photographs and young adult photographs. [5 the investigator's theory correct? Children Young Adult 65 80 67 69 53 7O 65 7O 67 6O 57 74 69 65 61 63 69 65 67 7O 56 80 65 79 57 69 63 75 53 62 58 73 55 71 61 68 66 7'5 6. A study was performed to test whether cars get better mileage on premium gas than on regular gas. Each of 6 cars was rst lled with either regular or premium gas, decided by a coin toss, and the mileage for that tank was recorded. The mileage was recorded again for the same cars using the other kind of gasoline. Is there evidence that the using premium gasoline is better? Regular = (16, 20, 21, 23, 22, 28) Premium = (19, 22, 24, 25, 25, 32)