III. (7 pts) Dr. Isbad conducted a psychophysics experiment to measure the faint
ID: 3501534 • Letter: I
Question
III. (7 pts) Dr. Isbad conducted a psychophysics experiment to measure the faintest sound a person can hear. He wanted to get a precise estimate of this terminal threshold, so he decided to use the method of limits staircase method. Below are the data from his subject. Dr. Isbad claims that the terminal threshold for all human hearing is 29. List and explain all the problems and errors committed by Dr. Isbad. Do you accept the value he obtained for his threshold? Why or why not? Given his data, what is the threshold value?
Trial
Stimulus
Response
1.
40
Yes
2.
15
No
3.
35
Yes
4.
30
Yes
5.
20
No
6.
15
No
7.
15
No
8.
20
No
9.
35
Yes
10.
10
No
11.
5
No
12.
15
No
13.
35
Yes
14.
30
Yes
15.
40
Yes
16.
30
No
17.
35
Yes
18.
5
No
19.
35
Yes
20.
10
No
21.
5
No
22.
20
No
23.
40
Yes
24.
10
No
25.
5
No
26.
20
No
27.
10
No
28.
40
Yes
29.
15
No
30.
20
No
31.
40
Yes
32.
30
Yes
33.
40
Yes
34.
10
No
35.
30
Yes
Trial
Stimulus
Response
1.
40
Yes
2.
15
No
3.
35
Yes
4.
30
Yes
5.
20
No
6.
15
No
7.
15
No
8.
20
No
9.
35
Yes
10.
10
No
11.
5
No
12.
15
No
13.
35
Yes
14.
30
Yes
15.
40
Yes
16.
30
No
17.
35
Yes
18.
5
No
19.
35
Yes
20.
10
No
21.
5
No
22.
20
No
23.
40
Yes
24.
10
No
25.
5
No
26.
20
No
27.
10
No
28.
40
Yes
29.
15
No
30.
20
No
31.
40
Yes
32.
30
Yes
33.
40
Yes
34.
10
No
35.
30
Yes
Explanation / Answer
Dr. Isbad is supposed to follow the staircase method in which the intensity of a stimulus is reduced until the observer makes a mistake, at which point the staircase 'reverses' and intensity is increased until the observer responds correctly, triggering another reversal. However the data shows that this method was not followed and stimulus intensity was presented at random at times. For instance, on the first trial, he presented an intensity of 40. This should have been followed by an intensity of 35 in the next trial but Dr. Isbad presented a value of 15. Also, from the data we can see that the stimulus value of 25 has not been presented to the subject. Therefore, we cannot adequately calculate the terminal threshold.