2. Hypothesis tests about a population mean, population standard deviation known 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 loosened their standards for issuing credit cards since 2002. You collect a random sample of 100 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 x̄ x̄ = 722. 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: x̄ x̄ ≥ 731, Haa: x̄ x̄ < 731   H₀: µ < 731, Haa: µ ≥ 731   H₀: µ ≥ 731, Haa: µ < 731   H₀: µ ≤ 731, Haa: µ > 731     If the null hypothesis is true as an equality, the sampling distribution of x̄ x̄ is approximated by _____   distribution with_______    and a standard deviation of  _____  .   The value of the standardized test statistic is_________    .   Use the Distributions tool to help you answer the questions that follow. You conduct the hypothesis test using a significance level of α = 0.05. 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 ≤ –1.96 or z ≥ 1.96   Reject Haa if z ≤ -1.645   Reject H₀ if z ≤ -1.645   Reject H₀ if z ≥ -1.18     The p-value is _______   .   Using the critical value approach, the null hypothesis is ____   , because ______   . Using the p-value approach, the null hypothesis is  ____  , because ____   . Therefore, you _____    conclude that banks have loosened their standards for issuing credit cards since 2002.

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2. Hypothesis tests about a population mean, population standard deviation known

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 loosened their standards for issuing credit cards since 2002. You collect a random sample of 100 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 x̄ x̄ = 722. 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: x̄ x̄ ≥ 731, Haa: x̄ x̄ < 731
 
H₀: µ < 731, Haa: µ ≥ 731
 
H₀: µ ≥ 731, Haa: µ < 731
 
H₀: µ ≤ 731, Haa: µ > 731
 
 
If the null hypothesis is true as an equality, the sampling distribution of x̄ x̄ is approximated by _____   distribution with_______    and a standard deviation of  _____  .
 
The value of the standardized test statistic is_________    .
 
Use the Distributions tool to help you answer the questions that follow.
You conduct the hypothesis test using a significance level of α = 0.05. 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 ≤ –1.96 or z ≥ 1.96
 
Reject Haa if z ≤ -1.645
 
Reject H₀ if z ≤ -1.645
 
Reject H₀ if z ≥ -1.18
 
 
The p-value is _______   .
 
Using the critical value approach, the null hypothesis is ____   , because ______   . Using the p-value approach, the null hypothesis is  ____  , because ____   . Therefore, you _____    conclude that banks have loosened their standards for issuing credit cards since 2002.

 

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