12 . The weight of a wooden block , in grams , selected from a factory is studied . A sample of 12 observations is recorded as below :
700 , 698 , 692 , 685 , 637 , 671 , 654 , 651 , 695 , 608 , 624 , 641
( a ) Find an unbiased estimate of the population mean .
( b ) Find sn
� 1.
( c ) Construct a 99 % confidence interval for the population mean , giving the answer to two decimal places .
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