1. Everitt, as reported in Hand et al. (1994), presented data on the amount of weight gained by 17 anorexic girls under one of three treatment conditions. One of the conditions were Cognitive Behavior Therapy. The weight gain of each anorexic girls who received cognitive behavioral therapy, What null hypothesis would we be likely to test in this situation?
The researcher considers that the program was successful with respect to gaining weight in the girls if on average it is more than 3 pounds.
2. A researcher investigating the effectiveness of different forms of advertising randomly selects ten subjects to take part in an experiment to determine if reaction time to a visible stimulus is different from reaction time to an audible stimulus. The null hypothesis (Ho) in this case is that there is no difference between reaction time to visual and auditory stimuli. The data are set in the following table:
Subjects A B C D E F G H I J
Reaction time to visual stimulus
(m. secs) 259 275 304 285 288 314 291 304 285 246 Reaction time to
auditory stimulus
(m. secs) 201 198 245 287 190 250 285 295 231 201 ID 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Gain 1.7 0.7 -0.1 -0.7 -3.5 14.9 3.5 17.1 -7.6 1.6 11.7 6.1 1.1 -4.0 20.9 -9.1 2.1
3. The data are from study involving the emotionality of children from lone-parent and two-parent families. The independent variable is family type which has two levels (the lone-parent type and two-lone-parent type. The dependent variable is emotionality on a standard psychological measure- in score. Is there a significance different between the two groups in terms of their emotionality?
3 4. A company wants to study the effect of the break from work on the productivity of their workers. Select 5 workers and their productivity measured in an ordinary day, and then measure the productivity of workers in the same 5 day granting the break from work. The measured productivity figures are as follows:
Do they indicate these results that the break from work increase productivity?
•Conduct the appropriate statistical test of your
hypothesis, using a
significance level = 0.05.
Dr. Rosa Padilla de Casamayor
Two-parent family 12 18 14 10 19 8 15 11 10 13 15 16
Lone-parent family 6 9 4 13 14 9 8 12 11 9
Without pause 23 35 29 33 43 With pause 28 38 39 37 42
5. They have total cholesterol levels of a sample of eight patients before and after participating in a diet-exercise program. Can be concluded that the program had positive impact?
Patient 1 2 3 4 5
Before 201 231 221 260 228
After 200 236 216 233 224
4 6. Do athletes in different sports vary in terms of intelligence? Bellow is reported College Board
scores of random samples of colleges’ basketball and football players. Is there a significant difference?
Conduct the appropriate statistical test of your hypothesis, using a significance level = 0.05
Dr. Rosa Padilla de Casamayor Basketball players 90 70 55 60
Football players 95 60 45 49
7. A Social Work Department wishing to validate an empathy scale gives the measure to intending Social workers and to a group of student matched by age and sex whose career choices are other than Social Work. The following table shows the scores of the two groups on the empathy measure. Do the scores indicated that intending Social Workers have higher empathy scores than non-Social Workers? The null hypothesis in this case is that there is no significant difference between the two groups. Answer: t= 5.243, Sig.=.000 (Check assumptions)
Social workers 80 79 78 69 68 78 75 74 73 81
Non-social worker 68 71 58 62 52 67 63 70 59 61
8. A researcher might compare the amount of bulling in two schools, one with a strict and punitive policy and the other with a police of counseling on discipline infringements. A sample of children from each school is interviewed and the number of times they have been bullied in the previous school year obtained. The independent variable is policy on discipline (which has two levels year obtained. The independent variable is policy on discipline (which has two levels – strict versus counseling); and the dependent variable is the number of times a child has been bullied in the previous school year.
Answer: t= -.178, Sig. = .870 Is a difference significantly between the two groups of scores?
Assignment 3
Strict policy 8 5 2 6 7
5 Dr. Rosa Padilla de Casamayor
a. Is a difference significantly between the two groups of scores? Answer: F=47.286, sig .000
b. Which differences are significant?
Assignment 3
9. Three groups of students involved in the same curriculum are obliged to study for 15 minutes, 30 minutes, or 90 minutes a night for 8 weeks before taking a mathematics test. Their scores are as follows:
a.Are the differences statistically significant? Answer: F=4.57, sig .033
b.If F is significant, which group(s) is(are) significantly different from which? (15’ compare 90’) c.How much of the difference in mathematics performance can be explained by how long students study?
d.What is the independent variable?
e.What is the data scale of the independent variable? f.What is the dependent variable?
g.What is the data scale of the dependent variable?
10. Here are the number of errors on an analysis of variance problem for each of nine students after drinking grape Kool-Aid, Frankenberry Punch, or water.
H2O GKA FBP
5 8 10
3 7 11
4 7 12
15 minutes 43 39 55 56 73
30 minutes 55 58 66 79 82