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A biologist wants to test the null hypothesis that the mean mean wingspan of a certain kind of insect is 12.3mm against the altenative that it is not 12.3 mm.
Directional and nondirectional hypotheses can be easily interchanged according to the hypothesis the researcher is testing. For instance, a drug company might predict that a drug will help a subject
A botanist wishes to test the null hypothesis that the average diameter of the flowers of a particular plant is 9.6cm. He decides to take a random sample of size n=80 and accept the null hypottesis
The Toylot company makes an electric train with a motor that it claims will draw an average of only 0.8 ampere (A) under a normal load. A sample of twelve motors was tested, and it was found that th
What is the value of the sample test statistic? (Round your answer to two decimal places.) Find the P-value. (Round your answer to four decimal places.)
If 9 square meters are chosen at random for a mosquito count, find the probability that the average of those counts is more than 73.6 mosquitos per square meter. Assume that the variable is normally
The mean weight of loads of rock is 49.0 tons with a standard deviation of 12.0 tons. If 9 loads are chosen at random for a weight check, find the probability that the mean weight of those loads is
Test the hypothesis that the average price is higher than $2.57. Use level of significance a = 0.05.
A charity receives 1700 contributions. Contributions are assumed to be independent and identically distributed with mean 2945 and standard deviation 150. Calculate the approximate 90th percentile fo
Suppose a manufacturing company makes a certain item. The time to produce each item is normally distributed around a mean of 157 minutes with a standard deviation of 46 minutes.
Suppose an x distribution has mean μ = 4. Consider two corresponding x distributions, the first based on samples of size n = 49 and the second based on samples of size n = 81.
1. In a recent survey of 4513 college undergraduates, 20% reported having fallen asleep in class. To test this result, your instructor sampled 25 students from his class and asked them if they
If when determining the cross-products for your correlation coefficient, positive z scores on one variable go with negative z scores on the other variable and negative z scores on one variable go wi
Which of the following correlation coefficients represents the variables with the weakest degree of relationship?
A survey of an urban university (population of 25,450) showed that 750 of 1100 students sampled attended a home football game during the season. Using the 99% level of confidence, what is the confid
A researcher notes that the correlation in the group she studies is so large that if there were not a correlation among people in general, there is less than a 5% chance of getting her correlation.
Annual starting salaries for college graduates with degrees in business adminstration are generally expected to be between $30,000 and $45,000 with a population standard deviation of $3750. Assume t
The lifetime of a disposable water filter is normally distributed with mean m = 30 gallons and standard deviation s = 6 gallons. What is the probability that a filter selected at random will last fr
Messages arrive at an interactive message center according to a counting process with the average inter-arrival time of 15 seconds. Choosing a frame size of 5 seconds, compute the probability that d
A student has computed that it takes an average (mean) of 16 minutes with a standard deviation of 3 minutes to drive from home, park the car, and walk to an early class. One day it took the student
A motel accepts 340 reservations for 315 rooms on July 1, expecting 10 percent no-shows on average from past records. Use the normal approximation to the binomial to find the probability that all gu
Then respond to the following: What are some of the factors you would want to consider in assessing such a difference in mortality? Discuss possible explanations as to why the crude mortality rate i
Let X1, X2 be a random sample of size 2 from a population X with E(X)=mu and V(X) = 36. Let T1 = (2X1 + X2)/3 and T2 = (3X1 - X2)/3 be two unbiased estimators for mu.
The compressive strengths of a random sample of 64 specimens of an alloy yielded sample average strength of 5566 psi and sample standard deviation of 82 psi. Find a 95% confidence interval for the t
The thickness of wafers in semiconductor manufacturing has a mean of 10 micrometers and standard deviation of 0.8 micrometers. Find approximate probability that the average thickness of 49 wafers ex