**2.2.3 Statistical analysis**

Statistical analysis was conducted to analyse the effect/relationship between independent variable and dependent variable. Non parametric statistic was implemented involving descriptive statistic and statistical binomial test. The tests were on hypotheses about the effect of each attributes or variables of the virtual environment on the incidence of visual symptoms. The hypotheses developed were:

Ergonomics Design Criteria of a Virtual Environment 175

and also in a comfortable posture while completing the virtual task. Participants were also

Table 1 shows the results of the experiment describing the effect of colour of the virtual background on visual symptoms of the subjects. There are five types of colour used in this experiment, which are Red, Fuchsia, Dark Sky Blue, Medium Slate Blue and White. The colours were identified on the basis of user's preferences. Statistical binomial test at 5% significant level shows that the overall background colour has an effect on the user i.e. eyestrain and blurred vision syndrome. The eyestrain syndrome was experienced by 75% of users when Red and White background colours were used while 63% was experienced by the users when Fuchsia, Dark Sky Blue and Medium Slate Blue background colours were used. The blurred vision syndrome was only experienced by users when Red background

**Proportion (%) Symptoms Exact Sig.** 

Eyestrain Dry and Irritated Eyes

Eyestrain Dry and Irritated Eyes Light Sensitivity

Eyestrain Blurred Vision

**Symptoms Exact Sig.** 

**(1-tailed) Decision** 

**(1-tailed) Decision** 

Effect Effect

Effect Effect Effect

0.534 0.169

0.178 0.138 0.169 Effect Effect

0.633 0.321

instructed to complete the questionnaire immediately after finishing the virtual task.

**3.1 Effect of colour of virtual background to visual symptoms** 

63

**Observation Proportion (%)** 

50

100 67 50

**2.** Fuchsia 63 Eyestrain 0.321 Effect **3.** Dark Sky Blue 63 Eyestrain 0.321 Effect

Table 1. Result of Experiment and Binomial Test of Visual Symptoms of Colour Virtual

**2.** 25% level 83 Eyestrain 0.534 Effect **3.** 50% level 83 Eyestrain 0.534 Effect

Table 2. Result of Experiment and Binomial Test of Visual Symptoms of Virtual Lighting

Blue 63 Eyestrain 0.321 Effect **5.** White 75 Eyestrain 0.633 Effect

**3. Results** 

colour was used.

**4.** Medium Slate

*p*> 0.05 ; N = 8

Background

**No. Level of** 

**4.** 100% level

*p*> 0.05 ; N = 8

**Brightness** 

**1.** 10% level <sup>83</sup>

**No. Colour Observation** 

**1.** Red <sup>75</sup>


The level of significance was set at α = 0.05 for all analyses.

#### **2.3 Experimental design and procedure**

#### **2.3.1 Experimental design**

The experiments were conducted at the ergonomic-virtual reality laboratory. A sitting position was adopted with the subject sitting at a distance of 15 – 25 cm from the back edge of the table to complete the task. The activity is to operate a virtual robot in the VE using an infrared mouse (wireless mouse) with the motion observed on the wide screen display.

The digital projector was positioned on a table 75 cm in height with an inclination angle of between 5o-10o with respect to the horizontal axis. The projector was connected to laptop with a display set to 1280 x 800 pixels. The distance from the front edge of the table or the digital projector to the center of the wide screen was 300 cm. The size of wide screen display is 170 cm in length and 155 cm in width. The bottom edge of wide screen display was measured at 94 cm above the floor. Prior to conducting the experiment, the subjects were made to adjust their seating positions to make them as comfortable as possible.

#### **2.3.2 Experimental procedure**

The subjects were provided with information describing the aims of the study and how the experiment will be conducted. Their health condition and past experience of sickness were also identified and their anthropometric data measured. The colour blind test was then conducted before proceeding to colour selection and the experiment. If a subject cannot complete the test, it means that the subject has some visual problems and is unable to continue the experiment.

Prior to performing the experiment, subjects were trained on how to use the wireless mouse in order to operate the virtual robot in the VE to complete the virtual task. Heart rate and visual acuity was measured before and after the experiment.

In the experiment, subjects were exposed to the virtual environment to view and operate a virtual robot by using a wireless mouse; to pick up a virtual material in a rack and to put it on a conveyor and subsequently to also pick up a virtual product on the conveyor and store in another rack as shown in Fig. 1. The activity was performed for 10 minutes for each attributes and for every subject of the VE studied. All subjects were required to sit in an upright posture and also in a comfortable posture while completing the virtual task. Participants were also instructed to complete the questionnaire immediately after finishing the virtual task.
