1. A school administrator is concerned about the amount of credit-card debt that college students have. She wishes to conduct a poll to estimate the percentage of full-time students who have credit-card debt of $2000 or more. What sample size should be obtained if she wishes the estimate to be within 2.2 percentage points with a 99% confidence if: Table of z*

90% 1.65

95% 1.96

98% 2.33

99% 2.58

a) a pilot study indicates that the percentage is 33.1%. ____________

b) no prior estimates are used.____________

2. A private opinion poll is conducted for a politician to determine what proportion of the population favors adding more national monuments. How large a sample is needed in order to be 90% confident that the sample proportion will not differ from the true proportion by more than 5%? a) a pilot study indicates that the percentage is 65%? ___________

b) no prior estimates are used. _______________

3, Many investors and financial analysts believe the Dow Jones Industrial Average (DJIA) gives a good barometer of the overall stock market. On January 31, 2006, 9 of the 30 stocks making up the DJIA increased in price (The Wall Street Journal, February 1, 2006). On the basis of this fact, a financial analyst claims we can assume that 30% of the stocks traded on the New York Stock Exchange (NYSE) went up the same day. A sample of 63 stocks traded on the NYSE that day showed that 23 went up. You are conducting a study to see if the proportion of stocks that went up is significantly more than 0.3. You use a significance level of=0.10. What is the test statistic for this sample? (Report answer accurate to 2 decimal places.)

test statistic =___________

What is the p-value for this sample? (Report answer accurate to 4 decimal places.)

p-value =_____________

As such, the final conclusion is that...

• There is sufficient evidence to warrant rejection of the claim that the proportion of stocks that went up is more than 0.3.
• There is not sufficient evidence to warrant rejection of the claim that the proportion of stocks that went up is more than 0.3.
• The sample data support the claim that the proportion of stocks that went up is more than 0.3.
• There is not sufficient sample evidence to support the claim that the proportion of stocks that went up is more than 0.3.
• A well-known brokerage firm executive claimed that 60% of investors are currently confident of meeting their investment goals. An XYZ Investor Optimism Survey, conducted over a two week period, found that in a sample of 500 people, 285 of them said they are confident of meeting their goals. Test the claim that the proportion of people who are confident is smaller than 60% at the 0.05 significance level. The null and alternative hypothesis would be:

H0:=0.6H0:=0.6 HA:>0.6HA:>0.6

H0:p=0.6H0:p=0.6 HA:p>0.6HA:p>0.6

H0:p=0.6H0:p=0.6 HA:p<0.6HA:p<0.6

H0:=0.6H0:=0.6 HA:0.6HA:0.6

H0:=0.6H0:=0.6 HA:<0.6HA:<0.6

H0:p=0.6H0:p=0.6 HA:p0.6HA:p0.6

The test statistic is:_______ (to 2 decimals)

The p-value is ____________ (to 4 decimals)

4."Trydint" bubble-gum company claims that 7 out of 10 people prefer their gum to "Eklypse". Test their claim at the 95-confidence level. The null and alternative hypothesis in symbols would be:

• H0:=0.7H0:=0.7 HA:0.7HA:0.7
• H0:=0.7H0:=0.7 HA:>0.7HA:>0.7
• H0:=0.7H0:=0.7 HA:<0.7HA:<0.7
• H0:p=0.7H0:p=0.7 HA:p0.7HA:p0.7
• H0:p=0.7H0:p=0.7 HA:p>0.7HA:p>0.7
• H0:p=0.7H0:p=0.7 HA:p<0.7HA:p<0.7 The null hypothesis in words would be:
• The proportion of all people that prefer Trydint gum is less than 0.7.
• The proportion of people in a sample that prefers Trydint gum is 0.7.
• The proportion of all people that prefer Trydint gum is greater than 0.7.
• The average of people that prefer Trydint gum is 0.7.
• The average of people that prefer Trydint gum is not 0.7.
• The proportion of people in a sample that prefer Trydint gum is not 0.7
• The proportion of all people that prefer Trydint gum is 0.7

Based on a sample of 270 people, 181 said they prefer "Trydint" gum to "Eklypse". The point estimate is__________ (to 3 decimals)

The 95 % confidence interval is ___________ to ____________ (to 3 decimals)