Table 4.

Multiple linear regression model summary and overall fit statistics.

Mode	R	R square	Adjusted R square	Std. error of the estimate
1	0.690a	0.476	0.417	61.916
2	0.690b	0.476	0.428	61.348
3	0.679c	0.461	0.422	61.650
4	0.663d	0.440	0.410	62.306

^aPredictors: average number of customers in a week, age of facility (beauty salon), number of services, temperature (°C), academic qualification, and years of working experience. ^bPredictors: average number of customers in a week, age of facility (beauty salon), number of services, temperature (°C), and academic qualification. ^cPredictors: average number of customers in a week, age of facility (beauty salon), number of services, and temperature (°C). ^dPredictors: average number of customers in a week, age of facility (beauty salon), and number of services. ^eDependent variable: formaldehyde concentration (CL (μg/m³)).