【問題】help ..help...

[xdongx 10]

1.The financial institutions in Alberta providing banking services (including credit unions and trust companies) are to be surveyed. Some of them are very large, with assets of more than $500 million; others are medium-sized, with assets between $100 million and $500 million; and the remaining have assets of less than $100 million. Explain how you would select a sample of these institutions.

2.The average mark (out of a maximum of 100) of a class of 300 students on a statistics examination is 68.2 with a standard deviation of 9.2. Suppose a random sample of marks of 40 students is selected using SRR. What is the probability that the sample mean will be

(a) less than 65?

(b) more than 72

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