1. (a) Eight randomly selected batches of a chemical were tested for impurity concentration. The percentage impurity levels found in the sample were as follows: 5.3 6.2 4.1 5.4 3.6 5.6 4.8 Calculate the sample mean and sample variance. Construct a 95% confidence interval for the population mean. 4.2 (0) (ii)

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1.
(a) Eight randomly selected batches of a chemical were tested for impurity
concentration. The percentage impurity levels found in the sample were as follows:
5.3 6.2 4.1 5.4 3.6 5.6 4.8
(b)
(c)
(d)
4.2
(0)
(ii)
Calculate the sample mean and sample variance.
Construct a 95% confidence interval for the population mean.
A random sample of 35 new graduates from Bangor University shows a mean
starting salary of £17,250 and a standard deviation of £3,088. Construct a 95%
confidence interval for the population mean starting salary.
A components manufacturer claims that its average proportion of defective
components is 1%. 65 defectives were found in a particular batch of 5000
components. Using the sample data, construct a 95% confidence interval for the
population proportion of defectives. Provide a recommendation as to whether or
not the company's claim should be believed.
A loan auditor at a bank wishes to consider the loan balance for all customers
who are currently carrying overdrafts. A random sample of 20 shows a sample mean
of £1559.42 and a sample standard deviation of £204.86. Assume that the balances
are normally distributed. Construct a 99% confidence interval for the population
mean balance, μx
Transcribed Image Text:1. (a) Eight randomly selected batches of a chemical were tested for impurity concentration. The percentage impurity levels found in the sample were as follows: 5.3 6.2 4.1 5.4 3.6 5.6 4.8 (b) (c) (d) 4.2 (0) (ii) Calculate the sample mean and sample variance. Construct a 95% confidence interval for the population mean. A random sample of 35 new graduates from Bangor University shows a mean starting salary of £17,250 and a standard deviation of £3,088. Construct a 95% confidence interval for the population mean starting salary. A components manufacturer claims that its average proportion of defective components is 1%. 65 defectives were found in a particular batch of 5000 components. Using the sample data, construct a 95% confidence interval for the population proportion of defectives. Provide a recommendation as to whether or not the company's claim should be believed. A loan auditor at a bank wishes to consider the loan balance for all customers who are currently carrying overdrafts. A random sample of 20 shows a sample mean of £1559.42 and a sample standard deviation of £204.86. Assume that the balances are normally distributed. Construct a 99% confidence interval for the population mean balance, μx
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