Lenders tighten or loosen their standards for issuing credit as economic conditions change. One of the criteria lenders use to evaluate the creditworthiness of a potential borrower is her credit risk score, usually a FICO score. FICO scores range from 300 to 850. A consumer with a high FICO score is perceived to be a low credit risk to the lender and is more likely to be extended credit than a consumer with a low score.
A credit card represents a line of credit, because the credit card holder obtains a loan whenever the card is used to pay for a purchase. A study of credit card accounts opened in 2002 found a mean FICO score for the credit card holder (at the time the card was issued) of 731 and a standard deviation of 76. [Source: Sumit Agarwal, John C. Driscoll, Xavier Gabaix, and David Laibson, “Learning in the Credit Card Market,” Working Paper 13822, National Bureau of Economic Research (NBER), February 2008.]
You conduct a hypothesis test to determine whether banks have tightened their standards for issuing credit cards since 2002. You collect a random sample of 64 credit cards issued during the past 6 months. The sample mean FICO score of the credit card holders (at the time their cards were issued) is x̄x̄ = 746. Assume that the standard deviation of the population of FICO scores for credit cards issued during the past 6 months is known to be σ = 76, the standard deviation from the NBER study.
Let µ equal the true population mean FICO score for consumers issued credit cards in the past 6 months. You should formulate the null and alternative hypotheses as:
H₀: µ ≤ 731, Haa: µ > 731
H₀: µ > 731, Haa: µ ≤ 731
H₀: x̄x̄ ≤ 731, Haa: x̄x̄ > 731
H₀: µ ≥ 731, Haa: µ < 731
If the null hypothesis is true as an equality, the sampling distribution of x̄x̄ is approximated bya normal distribution witha mean of 731 and a standard deviation of9.5 .
The value of the standardized test statistic isz = 1.58 .
Use the Distributions tool to help you answer the questions that follow.
Normal Distribution
Mean = 730
Standard Deviation = 8.5
710720730740750x̄z-2-1012z
You conduct the hypothesis test using a significance level of α = 0.10. Use the tool to develop the rejection region for your test. According to the critical value approach, when do you reject the null hypothesis?
Reject H₀ if z ≤ 1.58
Reject H₀ if z ≥ 1.282
Reject Haa if z ≥ 1.282
Reject H₀ if z ≤ –1.645 or z ≥ 1.645
The p-value is0.0571 .
Using the critical value approach, the null hypothesis isnot rejected , because . Using the p-value approach, the null hypothesis isnot rejected , because . Therefore, youcannot conclude that banks have tightened their standards for issuing credit cards since 2002.
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Similar to this problem just different numbers
1)
H₀: µ ≤ 731, Haa: µ > 731
sample mean 'x̄= | 746.000 |
sample size n= | 64.00 |
std deviation σ= | 76.000 |
std error ='σx=σ/√n= | 9.5000 |
test stat z = '(x̄-μ)*√n/σ= | 1.58 |
Decision rule:reject Ho if test statistic z>1.282 |
p value = | 0.0571 |
Using the critical value approach, the null hypothesis is rejected because test staitsitc is higher than critical value
Using the p-value approach, the null hypothesis is rejected because p value is less than 0.10
Therefore, you can onclude that banks have tightened their standards for issuing credit cards since 2002.
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