*2.2. Methodology of Identifying Methods of Reducing Construction Waste with Regards to the Size of the Enterprise*

In the subject literature review, the correlation analysis of two variables is especially popular [34–36]. In the presented paper, the subject of the study is to determine the relationship between the method of reducing construction waste in relation to a given construction product and the size of the construction enterprise. For this purpose:

• The answers of the respondents concerning the applied methods of waste reduction were qualified into five groups with regards to particular construction products. Each of these groups represented a certain size of an enterprise. In each group, the number of positive answers (YES) and the number of negative answers (NO) were determined;


$$\chi^2 = \sum\_{i=1}^{r} \sum\_{j=1}^{c} \frac{\left(O\_{ij} - E\_{ij}\right)^2}{E\_{ij}} \,. \tag{1}$$

where:

*χ*2—chi-square statistic,

*Oij*—observed counts obtained from surveys,

*Eij*—theoretical counts,

*r*—number of levels of variable X (X = 5) (number of enterprise groups), and *c*—number of levels of variable Y (Y = 2) (number of possible answers).

Chi-square statistics were calculated using the SPSS-26 computer program. The chisquare statistic has a distribution of *<sup>χ</sup>*<sup>2</sup> with (r − 1)(c − 1) degrees of freedom. In the analyzed case, the number of degrees of freedom is 4. The *p* value determined for the chi-square test statistic is compared with the significance level α. The critical significance level of α = 0.05 was adopted in the analyzes.

The null hypothesis *H*<sup>0</sup> and the alternative hypothesis *H*<sup>1</sup> were formulated:


where:

*p*—the probability (the value of *p* is compared to the theoretical value of α) α—the significance level.

If *p* > α ⇒ it can be assumed that there are no reasons to reject hypothesis *H*0. This means that there is no significant relationship between the size of the enterprise and the use of the analyzed method of reducing construction waste. The result is statistically insignificant.

If *p* ≤ α ⇒ it can be assumed that there are reasons for rejecting hypothesis *H*0. Based on the tested sample, it can be assumed that there is a relationship between the size of the enterprise and the use of the analyzed method of reducing construction waste. The result is statistically significant.

#### **3. Results**

Calculations of the chi-square test were performed for all the tested methods of reducing construction waste in relation to all the analyzed construction products. Table 4 only presents those results that are statistically significant, namely the statistics of frequency and percentage rates of YES and NO responses as well as the calculated values of the *χ*<sup>2</sup> (4) test and probability *p*. Other calculation results, which are not included in the table below, show that there is no significant relationship between the size of the enterprise and the use of the analyzed method of reducing construction waste.


**Table 4.** The statistics of the chi-square test and probability *p* of the occurrence of methods of reducing construction waste that were used by construction companies, with their size also provided.

#### **4. Discussion**

The analysis of the results of the calculations included in Table 4 helped to indicate methods of reducing waste, the application of which depends on the size of the construction company, to be indicated with a probability greater than 0.95. A significant statistical dependence was found for seven methods of reducing construction waste, namely appropriate storage, employee training in the field of waste management, use of monitoring systems, appropriate transport and unloading of products, appropriate involvement of subcontractors, use of prefabricated elements, and the reuse of products on the construction site. In all these cases, the statistic *Chi*2(4) > 9.487, and *p* < 0.05. No statistically significant correlation was found for the other six methods of reducing construction waste, namely ordering products to size and in the appropriate quantity, the security of the construction site, waste segregation on the construction site, the designation of a place for waste segregation on the construction site; timely delivery, and having a waste disposal plan. In all these cases, the value of the statistic *Chi*2(4) > 9.487, and *p* > 0.05. This means that the application of a given reduction method does not depend on the size of the enterprise. A detailed summary of the test results is provided in Table 5.


#### **Table 5.** Summary of research results.

Table 6 lists the construction products for which a statistically significant correlation was found between the method of reducing construction waste and the size of the enterprise. Moreover, for each construction product, the strength of this relationship (*PW*) was determined. The frequency of the affirmative answer (YES) indicated by the respondents was adopted as a measure of this strength. The following designations were adopted:

*PW* = 1 when the frequency is ≤60%,

*PW* = 2 when the frequency is between 61% and 75%, and

*PW* = 3 when the frequency is between 76% and 100%

**Table 6.** Construction products for which a statistically significant correlation was found between the method of reducing construction waste and the size of the construction enterprise.



#### **Table 6.** *Cont.*

Based on the results of the research, the following conclusions were drawn:

	- Appropriate storage in the case of steel and concrete;
	- Training of employees in the field of waste management in the case of steel, concrete, and wood;
	- Appropriate transport and unloading of products in the case of steel, concrete, and wood;
	- Appropriate involvement of subcontractors in the case of concrete and ceramic and stone tiles;
	- Use of prefabricated elements in the case of concrete, wood, and ceramic and stone tiles; and
	- Reuse of products on site in the case of steel.
	- 3.1. In enterprises employing 250 or more employees, the following methods are used:
		- 3.1.1. Most often (PW = 3):
			- Appropriate storage in relation to small-sized products, wood, and ceramic and stone tiles;
			- Training of employees in the field of waste management in the case of small-sized products;
	- Use of monitoring systems in the case of small-sized products and wood;
	- Appropriate involvement of subcontractors in the case of steel products; and
	- Reuse of products on the construction site in the case of smallsized products and wood.
	- Use of prefabricated elements in relation to steel and small-sized products;
	- Reuse of products on the construction site in the case of concrete products and ceramic and stone tiles.
	- 3.2.1. Most often (PW = 3):
		- Appropriate storage with regards to small-sized products, wood, and ceramic and stone tiles;
		- Training employees in the field of waste management with regards to small-sized products;
		- Use of monitoring systems in relation to all the groups of analyzed construction products;
		- Appropriate transport and unloading of products with regards to small-sized products;
		- Appropriate involvement of subcontractors with regards to steel products; and
		- Reuse of products on the construction site with regards to concrete, small-sized products, wood, and ceramic and stone tiles;
	- 3.2.2. Often (PW-2):
		- No such cases were observed.
	- 3.2.3. Rare (PW = 1):
		- Appropriate involvement of subcontractors with regards to smallsized products and wood;
		- Use of prefabricated elements with regards to steel and smallsized products.
	- 3.3.1. Most often (PW = 3):
		- No such cases were observed.
	- 3.3.2. Often (PW-2):
		- Appropriate storage with regards to wooden products;
		- Use of monitoring systems with regards to steel, concrete and wooden products;
		- Appropriate involvement of subcontractors with regards to steel and wooden products; and

• Reuse of products on the construction site with regards to wood, and ceramic and stone tiles.

3.3.3. Rare (PW = 1):

	- 3.4.1. Most often (PW = 3):
		- No such cases were observed.
	- 3.4.2. Often (PW-2):
		- Appropriate storage with regards to wood and ceramic and stone tiles;
		- Training employees in the field of waste management with regards to small-sized products;
		- Appropriate transport and unloading of products with regards to small-sized products; and
		- Reuse of products on the construction site with regards to concrete products.
	- 3.4.3. Rare (PW = 1):
		- Appropriate storage with regards to small-sized products;
		- Use of monitoring systems with regards to all the groups of analyzed construction products;
		- Appropriate involvement of subcontractors with regards to steel, small-sized, and wooden products;
		- Use of prefabricated elements with regards to steel and small-sized products; and
		- Reuse of products on the construction site with regards to smallsized products, wood, and ceramic and stone tiles.
	- 3.5.1. Most often (PW = 3):
		- Appropriate transport and unloading of products with regards to small-sized products;
		- Reuse of products on the construction site in relation to concrete, small-sized, and wooden products.
	- 3.5.2. Often (PW-2):
		- Reuse of products on the construction site with regards to ceramic and stone tiles.
	- 3.5.3. Rare (PW = 1):

#### **5. Conclusions**

The subject of the study was to determine the relationship between 13 methods of reducing construction waste and the size of the construction enterprise in relation to selected construction products. The selected construction products included steel, concrete, small-sized products, wood, and ceramic and stone tiles. Enterprises were divided into groups according to the number of employees, namely from 1 to 9 employees, from 10 to 49 employees, from 50 to 99 employees, from 100 to 249 employees, and for 250 employees and more. Employee surveys were conducted in enterprises belonging to the designated groups. The values of the chi-square test for the significance level of 0.05 and the degree of freedom 4 confirmed a statistically significant correlation between the size of the enterprise and seven methods of reducing construction waste, which included appropriate storage, the training of employees in waste management, the use of monitoring systems, the appropriate transport and unloading of products, the appropriate involvement of subcontractors, the use of prefabricated elements, and the reuse of products on the construction site. The dependence between the use of waste-reduction methods and the size of the enterprise did not always apply to all tested construction products, e.g., no statistically significant correlation was found in relation to steel and concrete in the case of the appropriate storage method. For the remaining six methods of reducing construction waste, no statistical correlation was found between the application of these methods and the size of the enterprise, but this does not mean that these methods were not used. The use of these methods or their non-application may be influenced by other factors that are not included in these studies.

In further research, it is recommended to focus on behavioral motives that can have a large impact on the use of methods that reduce construction waste in construction enterprises.

Studies presented in this paper make a significant contribution to the existing research concerning the reduction of construction waste. In conclusion, based on the conducted research, it was found that the bigger the enterprise, the more methods of reducing construction waste were applied. It can be assumed that larger construction enterprises have more human resources and financial support to plan, organize, and implement more methods of reducing construction waste than smaller enterprises. Therefore, it is crucial that governmental bodies will support reduction of construction waste by providing necessary trainings and financial support and will effectively require it. Thus, the presented analysis emphasizes the urgent need to improve, integrate, and adjust the promotion of the reduction of construction waste and the benefits of this reduction in construction enterprises, especially those of the smallest size.

**Author Contributions:** Conceptualization, M.B.; methodology, M.B. and B.H.; software, B.H.; validation, M.B. and B.H.; formal analysis, M.B. and B.H.; investigation, M.B.; resources, M.B.; data curation, M.B.; writing—original draft preparation, M.B.; writing—review and editing, B.H.; supervision, B.H. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study.

**Data Availability Statement:** All data included in this study are available upon request by contact with the corresponding author.

**Conflicts of Interest:** The authors declare no conflict of interest.
