We will determine the wavelength through the relationship given by the distance between slits, this relationship is given under the function

Here,
m = Number of order bright fringe
= Wavelength
d = Distance between slits
Both distance are the same, then



Rearranging to find the second wavelength




Therefore the wavelength of the light coming from the second monochromatic light source is 550.3nm
It increases confidence because the more times you conduct the same experiment over and over should either prove your hypothesis right and wrong and eliminate any random occurrences that might affect your results.