b) A survey of 672 audited tax returns showed that 448 resulted in additional
payments. Construct a 95% confidence interval for true percentage of all audited tax return that resulted in additional payments.
c) A packaging device is set to fill detergent powder packets with a mean weight of 5 kilogram and standard deviation of 0.21 kilogram. The weight of packets can be assumed to be normally distributed. The weight of packet is known to drift upwards over a period of time due to machine fault which is not tolerable. A random sample of 100 packets is taken and weighted. The sample has a mean weight of 5.03 kilogram. Can we conclude that the mean weight produced by machine has increased? Use 5% level of significance.