A company has been working to decrease the proportion of defective items among those delivered to one of its major buyers. The specifications set by this purchaser for a certain quality characteristic are within 20.0+or- 0.3 units. The following measurements have been reported for a sample of 50 items:

a) Find a 90% confidence interval for the proportion of nonconforming items.

b) Find a 95% confidence interval for the proportion of nonconforming items.

c) Can we conclude that the percent nonconforming of all items delivered to the current buyer is more than 13%? Use a level of significance 0.05.

20.10 19.75 20.20 20.15 19.90 20.00 19.65 19.92 19.80 20.13 19.98 20.05 20.20 20.23 20.31 20.01 20.49 19.99 20.13 20.18 20.03 19.87 19.93 20.11 20.22 19.84 20.12 20.24 20.03 20.08 20.00 20.11 20.99 20.33 20.11 19.89 20.32 19.76 20.05 19.97 20.05 19.85 19.87 19.67 20.06 19.95 20.09 20.10 19.90 19.73