Assignment

1) The historical output b employees is a mean of 120 units per hour with a standard deviation of 28 units. A new employee is tested on 30 different random occasions and is found to have an output of 107 units per hour. Does this indicate that the new employee's output is significantly different from the population mean output?

2) A mobile phone company is concerned at the lifetime of phone batteries supplied by a new supplier. Based upon historical data this type of battery should last for 900 days with a standard deviation of 150 days. A recent, randomly selected sample of 40 batteries was selected and the sample battery life was found to be 942 days. Is the sample battery life significantly different from 900 days (at the 5% significance level)?

3) Boys of a certain age are known to have a mean weight of μ = 85 pounds. A complaint is made that the boys living in a municipal children's home are underfed. As one bit of evidence, n = 25 boys (of the same age) are weighed and found to have a mean weight of 80.94 pounds. It is known that the population standard deviation σ is 11.6 pounds. Based on the available data, what should be concluded concerning the complaint? (For an alpha of 0.05.)

4) A school principle claims that the students in her school are of above average intelligence. A sample of 24 students has scored an average of 107.5 IQ points. The population average is 100, with a standard deviation of 15. Do we have sufficient evidence to support her claim? (At a 5% significance level.)

5) In a vocabulary test, the mean score was 68 with a standard deviation of 13. A class of 19 has a mean score of 65. At a significance level of 5%, can we reject the notion that this particular class is a typical one?