Chapter 6: Q7E (page 339)
Explain the difference between an interval estimator and a point estimator for
Short Answer
A random variable is an estimator, as well as a value, is an estimation that represents the estimator's calculated number.
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Chapter 6: Q7E (page 339)
Explain the difference between an interval estimator and a point estimator for
A random variable is an estimator, as well as a value, is an estimation that represents the estimator's calculated number.
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Lobster trap placement. Refer to the Bulletin of MarineScience(April 2010) study of lobster trap placement,Exercise 6.29 (p. 348). Recall that you used a 95% confidenceinterval to estimate the mean trap spacing (in meters)for the population of red spiny lobster fishermen fishing inBaja California Sur, Mexico. How many teams of fishermenwould need to be sampled in order to reduce the width ofthe confidence interval to 5 meters? Use the sample standarddeviation from Exercise 6.29 in your calculation.
Question: Let t0 be a specific value of t. Use Table III in Appendix D to find t0 values such that the following statements are true.
Question: A random sample of n measurements was selected from a population with unknown meanand known standard deviation. Calculate a 95% confidence interval forfor each of the following situations:
a. n = 75, = 28,= 12
b. n = 200, = 102, = 22
c. n = 100, = 15,=.3
d. n = 100, = 4.05, = .83
e. Is the assumption that the underlying population of measurements is normally distributed necessary to ensure the validity of the confidence intervals in parts a鈥揹? Explain.
Evaporation from swimming pools. A new formula for estimating the water evaporation from occupied swimming pools was proposed and analyzed in the journal Heating Piping/Air Conditioning Engineering (April 2013). The key components of the new formula are number of pool occupants, area of pool鈥檚 water surface, and the density difference between room air temperature and the air at the pool鈥檚 surface. Data were collected from a wide range of pools for which the evaporation level was known. The new formula was applied to each pool in the sample, yielding an estimated evaporation level. The absolute value of the deviation between the actual and estimated evaporation level was then recorded as a percentage. The researchers reported the following summary statistics for absolute deviation percentage: , . Assume that the sample contained swimming pools
a. Estimate the true mean absolute deviation percentage for the new formula with a 90% confidence interval.
b. The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) handbook also provides a formula for estimating pool evaporation. Suppose the ASHRAE mean absolute deviation percentage is . (This value was reported in the article.) On average, is the new formula 鈥渂etter鈥 than the ASHRAE formula? Explain
Use Table III, Appendix D to determine the values foreach of the following probability statements and their respectivedegrees of freedom (df ).
a.
b.
c.
d.
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