Question 2

Question

The science of ergonomics studies the influence of “human factors” in technology, i.e. how human beings relate to and work with machines. With widespread use of computers for data processing, computer scientists and psychologists are getting together to study human factors. One typical study investigates the productivity of secretaries with different word processing programs. An identical task was given to 18 secretaries, randomly allocated to three groups. Group 1 used a menu-driven program. Group 2 used a command-driven program, and Group 3 used a mixture of both approaches. The secretaries all had about the same level of experience, typing speed, and computer skills. The time (in minutes) taken to complete the task was observed. The results were as follows:


Group 1

Group 2

Group 3

Total

Menu-driven

Command-driven

Mengsel / Mixed



12

14

10



16

10

8



10

14

10



12

12

10



10

10

8



16

14

4



n1 =

n2 = A

n3 =

N = B

R1 =

R2 =

R3 = C

G = D

The following partially completed ANOVA table was obtained for the above data.

ANOVA table:

Source

SS

df

MS

Fcalc

Ftab

Treatments

H

J

34.8889

M

P

Error

84

15

L



Total

I

K





What is the value of C in the observation table?

Answer 1

To find the value of \( C \) (the total number of observations for each group), we need to first calculate how many secretaries (observations) there were in each group based on the provided data. From the data presented, we can see that there are three groups and each group contains data for 6 secretaries.

Specifically, the data provided is as follows:

• Group 1 (Menu-driven): 12, 16, 10, 12, 10, 16 (6 observations)
• Group 2 (Command-driven): 14, 10, 14, 12, 10, 14 (6 observations)
• Group 3 (Mixed): 10, 8, 10, 10, 8, 4 (6 observations)

Calculation:

Each group has:

• \( n_1 = 6 \) (Group 1)
• \( n_2 = 6 \) (Group 2)
• \( n_3 = 6 \) (Group 3)

Therefore, \( C \), which represents the total number of observations for each group, is \( C = 6 \).

So, the value of \( C \) in the observation table is \( 6 \).