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During a busy period at an airport, planes arrive at an average rate of 10 an hour. What is the probability distribution for the number of planes arriving in an hour?
Because the sample size is 64, do you need to be concerned about the shape of the population distribution when conducting the t test in (a)? Explain.
A machine makes a product, with 5% of units having faults. In a sample of 20 units, what is the probability that at least 1 is defective? In a sample of 200 units, what is the probability that at le
A set of observations follow a Normal distribution with mean 40 and standard deviation 4. What proportions of observations have values: (a) greater than 46, (b) less than 34, (c) between 34 and 46,
There is a 90% chance that the number of meals served in a week exceeds what value? There is a 90% chance that the number of meals served will fall within what range?
In estimating the 95% confidence interval estimate of the proportion of workers absent more than 10 days last year what is the upper limit of the confidence interval?
There are two coin purses. The first coin purse contains a penny (P) and a nickel (N). The second coin purse contains a dime (D) and a quarter (Q).
A machine makes parts with a variance of 14.5 cm in length. A random sample of 50 parts has a mean length of 106.5 cm. What are the 95% and 99% confidence intervals for the length of parts?
Is there evidence that the mean amount is different from 1.0 gallon (use alpha =0.01)? Compute the p-value and interpret its meaning.
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