Elk Density in Banff
Hebblewhite (2000) recorded the density (number per square km) of Elk (Cervus elaphus) in Banff National Park, Alberta, CA from 1986 to 2000. The raw data from his study are shown below. Further assume that it is known from previous studies that the standard deviation of density estimates for all years is 2 elk per square kilometer and the distribution is approximately normal. Use this information to construct and fully interpret a test, at the 10% significance level, of whether the mean density of elk is greater than 8 per square km.
5.20, 7.79, 6.46, 8.60, 8.97,8.65, 9.60, 9.09, 12.42,10.70,11.59,10.68,10.61,9.04,10.89
Credit Card Limits
Credit card companies use a regression model (includes such factors as income, employment, credit history) to determine the credit worthiness of a prospective card holder. In the past, the companies used a threshold (cutoff) limit of 630 to receive a card. It is also assumed that the standard deviation of all potential credit card holders is 5. Recent information suggests that delinquencies have been increasing and it is hypothesized that credit card companies will raise the “cutoff score” in response. Examine the following results concerning “cutoff scores” from 44 credit card issuers to determine, at the 10% level, if there is evidence that the “cutoff score” has been increased significantly from 630.
Variable Mean Median StDev Min Max Q1 Q3 CCards 636.86 636.50 4.42 629 647 633.25 640.00