GGR270H1 Final: Week 9 Study Notes

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tealwhale232

13 Dec 2010

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Ggr 270 lecture 9 november 10, 2010. To determine the level of precision of estimates, a confidence interval is placed around the sample. a properly created sample is essential for the successful application of inferential statistics. often, geographers want to know if a particular sample is representative of the population. Issue here may be to show that the sample differs significantly from the population. reject h0 as false, when in fact it is true. observing a difference when none actually exists. Fail to reject h0 when in fact it is false. Failing to observe a difference when one does exist. Test used is a function of the research question, and research assumptions. Tests will vary according to the number of samples drawn, sampling design, scale of information. one of the most com mon is the one-sample means test or one-sample difference of means test. placing a probability statement on the likelihood of sample error.

Related Questions

The average length of a roller coaster ride is 112 seconds with a known population standard deviation of 50.5 seconds. Suppose we take a sample of the last 100 roller coasters that were built and find that the average of those 100 is 105 seconds. We are interested in seeing if the actual average length of a roller coaster ride is significantly different than 112 seconds.

a. What is the standard error?

b. What is the margin of error at 90% confidence?

c. Using my sample of 100, what would be the 90% confidence interval for the population mean?

d. If I wanted to control my margin of error and set it to 5 at 90% confidence, what sample size would I need to take instead of the 100?

purplewhale646

The operations manager at a compact fluorescent light bulb (CFL) factory needs to estimate the mean life of a large shipment of CFLs. The manufacturer’s specifications are that the standard deviation is 1,000 hours. A random sample of 64 CFLs indicated a sample mean life of 7,500 hours.

a) Construct a 95% confidence interval for the population mean life of compact fluorescent light bulbs in this shipment.

b) Do you think that the manufacturer has the right to state that the compact fluorescent light bulbs have a mean life of 8,000 hours? Explain.

c) Must you assume that the population compact fluorescent light bulb life is normally distributed? Please explain.

azureferret234

The fish population P(t) in a lake is suddenly attacked by adisease that render the fish unable to reproduce. Assuming that thedeath rate of the fish is inversely proportional to the square rootof the fish population (i.e. k1 = Î²/â(P) where Î² is aconstant), perform the following tasks:

1. Write a differential equation that models the population offish as a function of time. Assume that the fish are infected bythe disease at t = 0 and define your constants.

2. Solve the differential equation with the initial condition thatP(0) = P0.

3. What is the half-life of the fish population?

4. If there were 900 fish initially, and 441 are left after 6weeks, how long does it take for all the fish to die? Assume thatthe disease was caused by radioactive waste dumped in the lake. Itis discovered that another population of fish, S(t), spontaneouslymutate into the original fish at a rate of k2 (per week) and neverdie. The population S(t) are born at a rate k3.

5. Draw a diagram that describes the life cycle of these twofish populations including your rate constants.

6. Write the differential equations describing the populationsof P(t) and S(t).

GGR270H1 Final: Week 9 Study Notes

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