Q2. Direct Mailing Company sells computers and computer parts by mail. The company claims that at least 90% of all orders are mailed within 48 hours after they are received. The quality control...

Bus-173 (Applied Statistics) :

Extracted text: Q2. Direct Mailing Company sells computers and computer parts by mail. The company claims that at least 90% of all orders are mailed within 48 hours after they are received. The quality control department at the company often takes samples to check if this claim is valid. A recently taken sample of 160 orders showed that 140 of them were mailed within 48 hours. (a) Mention required conditions of the large sample for testing proportion and check these for the above problem. (b) Test at 1% level of significance the hypothesis that the percentage of all orders are mailed within 48 hours is less than 90%.