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:

Question

Groep / Group 1

Groep / Group 2

Groep / Group 3

Totaal / Total

Menu-aangedrewe / Menu-driven

Opdrag-aangedrewe / 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

Die volgende gedeeltelik voltooide ANAVA tabel is vir die bostaande data verkry. / 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 A in the observation table? / Wat is die waarde van A in die waarnemingstabel?

Answer 1

To find the value of \( A \) (the sample size for Group 2), we first need to analyze the provided data.

The number of secretaries in each group is given as follows:

• Group 1 (Menu-driven): 6 observations
• Group 2 (Command-driven): 6 observations (This is what we need to verify)
• Group 3 (Mixed): 6 observations

Let’s count the observations for Group 2:

From the data provided, here are the times recorded for Group 2 (Command-driven):

• 16
• 10
• 14
• 12
• 10
• 14

Thus, we have a total of 6 observations for Group 2.

With that, we can conclude that \( A = 6 \).

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