The annual income of doctors constitutes a highly positive-skewed distribution. Suppose the population has an unknown mean and a standard deviation of £10,000. An estimate of the population mean is to...

The annual income of doctors constitutes a highly positive-skewed distribution. Suppose the population has an unknown mean and a standard deviation of £10,000. An estimate of the population mean is to be made using the sample mean. This estimate must be within £1000 either side of the true mean: (a) if n = 100, find the probability that the estimate will meet the desired accuracy and (b) if n = 625, find the probability that the estimate will meet the desired accuracy