1.

GSK Pharmaceuticals wish to ensure that their Paracetamol tablets contain, on average, the amount quoted on the packet of their product – namely 500 mg. Clinical tests on a random sample of 38 tablets yielded an average of 500.7 mg of Paracetamol per tablet. If it can be assumed,on the basis of previous trials, that the standard deviation of is 5 mg, construct a 99.5% confidence interval for the average amount of Paracetamol. State the lower limit (in mg) of this interval correct to two decimal places.

2.

A random sample of 57 children with working mothers showed that they were absent from school an average of 5.3 days per term with a standard deviation of 1.8 days. If days absent follows a normal distribution, determine the critical value for the test statistic (z or t) needed to build a 98% confidence interval for the average number of days absent per term for all children. State the positive value only exactly as found in the table (3 decimal places).

3.

An interval estimate for the average distance car tyres lasted during their “lifetime” was reported to be 33112 km to 36775 km. This interval estimate was based on a sample of 47 tyres. The variance of the lifetime was determined from previous studies to be 44885212 km squared. What level of confidence can be attributed to this interval estimate? State your answer as a percentage, correct to the nearest whole number.