practical problems

• cost: can we afford to complete the research? the larger the sample,the more time spent,the greater the expense.travelling is also expensive-can we complete the work where we already live?
• access: can we actually find a sample? sometimes the sample is not easy,because they don't want to speak to us(e.g criminals) whilst others have legal protection (e.g. children,vulnerable adults)
• time: we usually have limited time period to complete the research. the longer it takes,the more expensive it is. detail is time-consuming-qualitative data takes longer to study.