The company's chain stores have an average daily turnover of RMB 7,500 and a standard deviation of RMB 2,000. It is expe

[answerhappygod]

The company's chain stores have an average daily turnover of RMB
7,500 and a
standard deviation of RMB 2,000. It is expected that the
turnover will decrease
this year. 36 chain stores are randomly selected and the average
daily turnover is
calculated to be RMB 6,800. Assuming the standard deviation
remains
unchanged, let's ask
(a) With a significant level of 5%, has the average daily
turnover of the chain
store decreased?
(b) According (a), if the actual daily turnover is 7,000 yuan,
what is the value of
Type II error?
(c) Continue (b). If α and β are reduced to half of the original
at the same time,
how much does the number of samples need to increase?