Validity and reliability of a questionnaire developed to explore nutrition determinants among construction workers in Gauteng, South Africa

Figures & data

Table 1: Response rates from the selected sites

Description of setting		Distributed	Received
Building	Trading centre (new construction)	40	24
	Office property sites (new additions at basement stage)	60	47
	New hospital site (7 two-storey hospital buildings)	75	67
	Students’ residence (new construction)	16	16
	Residential property (renovation)	10	10
	Total	201	164
Road	One extension and two maintenance projects	19	19
Total		220	183

Table 2: Communalities

Measures	Initial	Extraction
What I know an adult should eat in a day	0.525	0.284
What I know would give me different nutrients, e.g. proteins, carbohydrates, vitamins and minerals	0.754	0.584
What I know will give me energy	0.708	0.694
What I know can happen to my health if I eat or don’t eat particular foods	0.635	0.480
What I know my body size needs	0.751	0.443
What I know my body needs at my age	0.687	0.547
What I know my body needs for my current health status	0.772	0.561
What I know my body needs for the type of work I do	0.611	0.421
What I know I should eat as a man or woman	0.738	0.557
My cooking skills	0.729	0.468
The wages I am paid	0.746	0.595
The foods available	0.719	0.637
The cost of the food	0.706	0.719
The way the food is advertised or marketed	0.735	0.481
The brand name	0.791	0.648
The foods on special offers or discounts	0.518	0.456
The location of where the food is sold	0.742	0.429
The food in season	0.754	0.580
The time I have before work and during breaks	0.770	0.642
The eating facilities provided on site, e.g. benches, tables, washing bowls/sinks, etc.	0.883	0.704
The facilities on site for storing and heating up my food	0.875	0.766
What my friends choose for us to eat	0.775	0.494
What I am used to from home and family traditions	0.596	0.294
Social media and networking	0.759	0.554
The need to belong to a particular social group	0.690	0.431
My belief that I should only eat food from my culture	0.760	0.597
My belief that killing animals for food is not good	0.790	0.566
My belief that avoiding meat will keep me healthier	0.822	0.663
My belief that avoiding meat will save me money	0.779	0.635
My belief that my current diet is adequate	0.560	0.285
The fact that healthy food will help increase my productivity at work	0.679	0.437
The fact that healthy food will help me concentrate on my work and avoid accidents and injuries	0.583	0.393
My idea that I will add or lose weight with particular foods	0.664	0.361
My idea that particular foods are advertised for the benefit of the sellers or advertisers	0.651	0.412
My mood, e.g. happy, sad, stressed, etc.	0.736	0.501
My eating habits, e.g. adding salt no matter what, having my food with beer or juice instead of water, eating something sweet after a meal, eating the same cereal every day	0.707	0.516
How hungry I am	0.744	0.513
The taste of the food	0.727	0.695
My appetite for particular foods	0.644	0.482
The feeling of fullness I get from the food	0.757	0.559
The quality of the food	0.719	0.407
How presentable the food is	0.720	0.601

Table 3: Loading matrix and percentage variance of the extracted factors after second run

Constructs	Measures	Factor 1	Factor 2	Factor 3	Factor 4	Factor 5	Factor 6	Factor 7
Food context	Brand name	0.726	0.180	0.065	0.074	−0.013	−0.153	−0.147
	Food in season	0.694	−0.027	−0.024	0.084	0.056	0.024	0.123
	Time I have before work and during breaks	0.551	0.051	0.017	−0.067	0.027	−0.134	0.373
	Location of where the food is sold	0.540	0.046	−0.065	0.118	−0.073	−0.123	0.064
	Cooking skills	0.482	−0.029	0.038	−0.061	0.078	0.013	0.369
	The way the food is advertised or marketed	0.469	0.178	0.020	0.133	−0.010	−0.158	0.121
	What I am used to from home and family traditions	0.279	0.113	−0.016	0.129	0.201	−0.137	0.106
Biological factors	The taste of the food	0.156	0.765	0.283	−0.093	−0.030	0.139	0.110
	my appetite for particular foods	0.186	0.623	−0.007	0.020	−0.081	−0.086	0.054
	How presentable the food is	−0.002	0.612	−0.323	0.067	−0.043	−0.243	0.122
	The feeling of fullness I get from the food	0.015	0.576	−0.046	0.005	0.346	0.060	0.012
	The quality of the food	−0.096	0.564	0.009	0.115	0.031	−0.142	−0.061
	how hungry I am	−0.016	0.507	0.108	0.149	0.307	0.158	0.057
Nutritional knowledge	What I know will give me energy	−0.177	0.046	0.786	0.085	0.172	0.149	0.074
	What I know would give me different nutrients, e.g. proteins, carbohydrates, vitamins and minerals	−0.123	0.105	0.721	0.069	−0.094	−0.163	−0.091
	What I know can happen to my health if I eat or don’t eat particular foods	0.228	0.206	0.427	−0.128	0.178	−0.270	−0.099
	What I know an adult should eat in a day	0.180	−0.138	0.404	−0.043	−0.030	−0.086	0.122
Personal ideas and systems	My eating habits, e.g. adding salt no matter what, having my food with beer or juice instead of water, eating something sweet after a meal, eating the same cereal every day	−0.058	0.256	−0.124	0.610	0.023	−0.010	0.038
	My idea that particular foods are advertised for the benefit of the sellers or advertisers	0.142	−0.206	0.084	0.574	0.165	−0.021	−0.088
	My mood, e.g. happy, sad, stressed, etc.	0.196	0.226	0.018	0.538	0.110	0.027	−0.075
	The fact that healthy food will help me concentrate on my work and avoid accidents and injuries	−0.331	0.020	0.064	0.521	0.104	−0.182	−0.092
	What my friends choose for us to eat	0.104	0.276	0.011	0.483	−0.036	0.075	0.213
	The need to belong to a particular social group	0.002	0.114	−0.068	0.471	0.013	−0.112	0.248
	Social media and networking	0.315	0.277	0.032	0.471	−0.102	−0.034	0.005
	My belief that avoiding meat will keep me healthier	0.204	−0.163	0.080	0.448	−0.278	−0.188	0.313
	My belief that killing animals for food is not good	0.328	−0.047	0.159	0.429	−0.106	0.043	0.268
	My belief that my current diet is adequate	0.072	−0.066	0.258	0.358	−0.114	−0.081	0.093
Economic factors	The cost/price of the food	0.049	−0.168	0.074	0.118	0.845	0.051	−0.127
	the foods available	0.062	0.074	−0.014	−0.249	0.729	−0.198	0.100
	The wages I am paid/income I make	−0.254	0.069	0.005	0.079	0.636	−0.154	0.233
	The foods on special offers or discounts	0.333	0.122	0.006	0.204	0.464	0.190	0.011
Resources	The facilities on site for storing and heating up my food	0.466	0.034	−0.100	0.106	0.041	−0.633	−0.065
	The eating facilities provided on site, e.g. benches, tables, washing bowls/sinks, etc.	0.355	0.033	0.074	0.120	0.042	−0.616	−0.026
	What I know my body needs for my current health status	0.174	0.036	0.237	−0.080	−0.071	−0.564	0.138
	What I know my body needs at my age	−0.114	−0.048	0.151	0.100	−0.062	−0.558	0.300
	The fact that healthy food will help increase my productivity at work	−0.188	0.131	0.055	0.073	0.232	−0.525	−0.112
	What I know my body size needs	0.144	−0.175	0.212	−0.059	0.074	−0.413	0.263
	My idea that I will add or lose weight with particular foods	0.047	0.173	−0.131	0.298	0.110	−0.318	0.020
Cultural distinctions	What I know I should eat as a man or woman	0.202	0.035	−0.002	−0.011	0.014	0.003	0.652
	What I know my body needs for the type of work I do	−0.222	0.232	0.109	−0.059	0.091	−0.062	0.560
	My belief that I should only eat food from my culture	0.109	0.027	0.049	0.396	0.015	0.022	0.515
	My belief that avoiding meat will save money	0.251	−0.206	−0.252	0.367	−0.097	−0.138	0.427
Eigen value		10.68	4.15	2.88	2.24	1.88	1.82	1.59
% variance explained by each factor		25.43	9.87	6.85	5.34	4.48	4.33	3.79
Cumulative %		25.43	35.30	42.15	47.49	51.97	56.30	60.09

Note: Items in bold italics show loading on each factor after extraction.

Table 4: Cronbach’s alpha and mean inter-item coefficients of the seven-factor solution

Factor		Alpha values	Mean inter-item correlations	Number of items
1	Food context	0.850	0.487	6
2	Biological factors	0.817	0.428	6
3	Nutritional knowledge	0.623	0.304	4
4	Personal ideas and systems	0.841	0.341	10
5	Economic factors	0.740	0.430	4
6	Resources	0.797	0.357	7
7	Cultural background	0.713	0.379	4