1- You are in charge of a new study on the effect of caffeine and memory. From , a previous pilot study , you find that the effect size is 0.6. You want to have a type I error at 0.05 and a type II error of 0.2 . In your study you split your sample in two independent groups of equal size ( control : no caffeinated; Experimental : with caffeine). How many people in total will you need to recruit?
2- Invent a fictional study where you have to decide if a group is better than the other. The significance level was set at 5%. Both groups are independent of one another. Show your reasoning.
|
Grp 1
|
Grp 2
|
|
Subject
|
Result
|
Subject
|
Result
|
|
S1
|
46.0
|
S13
|
44.0
|
|
S2
|
51.6
|
S14
|
48.9
|
|
S3
|
59.4
|
S15
|
41.9
|
|
S4
|
55.8
|
S16
|
53.9
|
|
S5
|
57.8
|
S17
|
44.9
|
|
S6
|
47.3
|
S18
|
44.7
|
|
S7
|
53.5
|
S19
|
39.5
|
|
S8
|
56.6
|
S20
|
47.3
|
|
S9
|
45.7
|
S21
|
46.7
|
|
S10
|
43.1
|
S22
|
44.9
|
|
S11
|
50.5
|
S23
|
55.2
|
|
S12
|
46.3
|
|
|
3- Data from a study on the number of weeks of practice the cha -cha-cha and the number of times per minute as our partner we walk on the feet are shown in the following table.
|
Subject
|
Nb. week
|
Nb . of times one has walk all over
|
|
S1
|
2
|
4
|
|
S2
|
5
|
3
|
|
S3
|
4
|
0
|
|
S4
|
0
|
6
|
|
S5
|
4
|
4
|
|
S6
|
1
|
10
|
|
S7
|
5
|
1
|
A) Following these comments, Is it worth it to take dance lessons? (Do not forget to include a graph).
B) After 8 weeks of practice, what is the predicted score?
4- You drive a study on the effect of a new ABC revolutionary way to increase memory performance in humans. To verify the effectiveness of this method, you have selected 12 subjects randomly drawn from a normally distributed population . At first , you measured the mnemonic performance issues on a routine task of nonsense words encoding for a period of 30 minutes . You recorded the performance of the subjects in the pretest column. Later, you have taught the new method to topics mnemonic ABC . Finally, to verify the effectiveness of the ABC method , you are re-measured performance subject to the same type of encoding task. The performance of subjects were then encoded in the post- test column. now you want to know if the ABC method is effective for a significance level of 5%
|
Subject
|
before-test
|
after-test
|
|
1
|
64
|
67
|
|
2
|
44
|
47
|
|
3
|
48
|
55
|
|
4
|
47
|
64
|
|
5
|
41
|
37
|
|
6
|
50
|
66
|
|
7
|
32
|
41
|
|
8
|
41
|
53
|
|
9
|
60
|
57
|
|
10
|
43
|
43
|
|
11
|
56
|
49
|
|
12
|
56
|
70
|
5- In a study on the role of music and the growth of tomato plants you planted 80 tomato plants. Half the plants grew without music, while the other half grew up with music. When the plants have reached full maturity you've measured and you got as average of 100 cm and 102 cm for the group without the group with music and music respectively. In addition, you have calculated the standard deviations of the two groups that are 9 cm for the group without music and 11 cm for the group with music. As the importance of this study is crucial for the future of the music world, you set your significance level 0.01.
However, after analysis you observe that tobs
6- A preliminary study on the use of virtual reality as a tool to cause anxiety among participants with obsessive compulsive disorder (OCD ) shows the following results: Table1. The mean ( and SD) the number of the front door verification events in patient with OCD ( n = 33) and healthy control group ( CS) in a virtual environment
|
|
OCD
|
CS
|
Statistic t
|
Value P
|
|
Nb.verification
|
139.7 (71.7)
|
93.8 (36.4)
|
-3.156
|
0.002
|
SD, standard deviation; OCD, obsessive compulsive disorder; CS, health control What percentage of variability explained? Show your reasoning.