Suppose a population of companies has a mean score of 400 and a standard deviation of 24 for their credit ratings. If a random sample of size 144 is drawn from the population, calculate the probability of drawing a sample of companies with a mean credit score between 395.5 and 404.5.
Below you are given ages that were obtained by taking a random sample of 6 MBA students. Assume the population has a normal distribution.
40 42 43 39 37 39A sample of 200 women from the labour force found an average wage of £6000 pa. with standard deviation £2500. A sample of 100 men found an average wage of £8000 with standard deviation £1500. Estimate the true difference in wages between men and women using a 95% confidence interval.
A different survey, of 50 men and 75 women doing similar jobs, found that women were paid on average £7200, with standard deviation £1225 and men were paid on average £7600 with standard deviation £750. Estimate the difference between male and female wages using these new data. What can be concluded from the results of the two surveys?
An IT manager considers that the average number of hits on the company intranet pages should be 75. The mean number of hits per week on a random sample of 60 pages is 71.4 with a standard deviation of 31.9. Is there sufficient evidence to support the IT manager’s claim using 95% confidence intervals?nfidence interval
It is claimed that the starting salary for Economics graduates in 2020/21 was £28, 000. A random sample of 50 Economics graduates in 2024, were asked for their starting annual salary. The mean salary was £32,200 with a standard deviation of £8,000. Is there sufficient evidence to suggest that the starting salary for economics graduates has increased?