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Sentinal Phoneback answers customer enquiries with telephone calls. When they timed a sample of 40 calls, they found a mean duration of 14.9 minutes and a standard deviation in duration of 2 minutes
A binomial process has a probability of success of 0.15. If eight trials are run, what are the mean number of successes and the standard deviation? What is the probability distribution for the numbe
In a town, 60% of families are known to drive European cars. In a sample of 10 families, what is the probability that at least 8 drive European cars? In a sample of 1,000 families, what is the proba
Construct a 95% confidence interval estimate of the population mean life of the light bulbs. Compare the results of (a) and (c). What conclusions do you reach?
If the company drills 12 wells, what is the probability that all 12 are producer wells? What is the probability that all 12 are dry wells? What is the probability distribution for the number of dry
At the 0.01 level of significance, is there evidence that reducing coffee prices is a good strategy for increasing the mean customer count?
The mean wage of people living in Alto Canillas is said to be £400 a week with a standard deviation of £100. A random sample of 36 people was examined. What is the acceptance range for a
Hamil Coaches Ltd say that their long-distance coaches take 5 hours for a particular journey. Last week a consumer group tested these figures by timing a sample of 30 journeys. These had a mean time
A food processor specifies the mean weight of a product as 200 g. A random sample of 20 has a mean of 195 g and a standard deviation of 15 g. Does this evidence suggest that the mean weight is too l
An emergency breakdown service suggests that 50% of all drivers are registered with their service. A random sample of 100 people had 45 who were registered. Does this sample support the original cla
Health service managers say that doctors should not spend more than 2 hours a day doing paperwork. A sample of 40 doctors spends an average of 2 hours 25 minutes a day doing paperwork, with a standa
A mobile phone has an advertised life of 30,000 hours. A sample of 50 phones had a life of 28,500 hours with a standard deviation of 1,000 hours. What can you say about the advertisements?
The number of road accident victims reporting to a hospital emergency ward is shown in the following table. Do these figures follow a Poisson distribution?
A frozen-food packer specifies the mean weight of a product as 200 g. The output is Normally distributed with a standard deviation of 15 g. A random sample of 20 has a mean of 195 g. Does this sugge
Hamil Sopa took a random sample of 60 invoices from his year's records. The mean value of invoices in this sample was £125.50 and the standard deviation was £10.20. What are the 90% and
A company wants to find the average weight of its products. A large initial sample shows the standard deviation of the weight is 20 g. What sample size would give a 95% confidence interval for the p
Last year a trial survey found that 65% of houses in Morrisey township had a computer. A follow-up survey wants to find the actual number of houses with a computer to within 3% with a 95% confidence
Wade (Retail) looked at a random sample of 100 invoices from a large population. Eight of these contained an error. What are the 90% and 95% confidence intervals for the proportion of invoices with
If the same results had been found from a sample of 20 pieces of equipment, what would be the 95% confidence interval? What would be the result if a Normal distribution had been used?
What is the weight Henry can be 95% confident the mean falls below? What are the two-sided confidence limits on this weight?
What is the number of defectives they can be 95% confident that the population mean is below? What is the number of defectives they can be 95% confident that the population mean is above? How do th
To reduce emergency room waiting times, the hospital improved patient check-in procedures, billing, record keeping, and laboratory processes. Acute-care beds are set aside for the real emergencies a
In the past, the proportion non-conforming has been 0.04. What is the probability that one of the fifteen samples taken today will contain an excessive amount of pollutants?
Four married couples have bought 8 scats in the same row for a concert. In how many different ways can they be seated?
A symphony orchestra has in its repertoire 30 Haydn symphonies, 15 modern works, and 9 Beethoven symphonies. Its program always consists of a Haydn symphony followed by a modern work, and then a Bee