Some people claim that about 20% of young people downloaded music from an Internet sitting not authorized by a record company. To verify this statement a survey was conducted on the 900 young Internet users. 

a) How is called a statistic which should be used to estimate the proportion of all young people downloading music illegally? 

Suppose that the population proportion is 20%. 

b) What are an expected value and a standard deviation of the statistic chosen in a)? 

c) What is its (approximated) probability distribution? 

d) Find probability that the consider proportion in our sample is between 15% and 2070 

e) Suppose that 30% of respondents admitted that they downloaded music from an Internet not authorized by a record company. Is it unexpected, given the supposition?