Problem 91 Rate of defective products A company claims that

Problem #9-1: Rate of defective products A company claims that only 3% of its products are defective. A simple random sample of 250 of their products yielded 8 defective items. Is there sufficient evidence from the sample data to suggest that the company\'s claim is too low? Problem #9-2: Part-time work habits It is believed that the mean number of hours of part-time work of high school seniors in a particular city is io.6 hours. Data from a simple random sample of 5o seniors indicated that their mean number of hours of part-time work was 12.5 with a standard deviation of 1.3. Test whether these data cast doubt on the accepted mean number of hours of work per week.

Solution

Problem # 9-1 )

Sample sixe =250

As per claim of the company , defective items = 3% of 250 = 7.5

And originally 8 items are defective .

Yes, it is sufficient evidence that the the company\'s clain is too low.

Problem # 9-2)

Sample space = 50

Mean for this sample space = 12.5

Therefore , standard deviation = sqrt( 50* (10.5 -12.5)^2 /50)

= 2

But given standard deviation is 1.3

Hence , these data castdoubt on the accepted mean number of hours of work per week.