More sentences : Please help

Would somebody help me with my English?

1- Not all concurrent diseases and medications which may induce seizure were identified.

2- Marketing strategies by the drug companies and their competitors in different countries are not the same. This may give some effects to the results of this type of study.

3- Differences in sample baseline: Some of the samples were specialist (40.3%) with difference specialties, and samples were from different geographical areas (Area 1 consists predominantly of old established suburbs and area 2 of relatively new suburbs and country areas). These might influence the study results.

4- No explanation given why some of the faculties and physicians did not give the response.

Thanks,

Dean