a sampling issue

[6stephen sands]

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Dear Sir/Madam,
I should be so grateful if you please could give me a simple answer for my 
following question. I have a sample which accounts for about 90% of the 
population. There was no possibility to include the rest (10%) because of 
lack of data. From a statistical point of view, Is it advantageous to have 
this large proportion which nearly the whole population.  How does this 
influence the inferences and conclusions? How different the way in which I 
look to P values in this case from that in which I have a sample of less 
percentage (Let�s assume that the missing firms from my sample are 
represented by similar firms have similar characteristics). (Statistical 
analysis used includes Kruskal-Wallis, Man-Whitney and Logistic regression). 
I would highly appreciate it if you please could state your answer in simple 
terms for a person who is not good at statistics? Thank you

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