1)Of 24,000 homes in a large suburban community, 4200 have one bedroom, 8400 have two bedrooms, 6400 have three bedrooms, 3200 have four bedrooms, and 1800 have five bedrooms. If one of the homes is selected at random, what is the probability that it has 3 or 4 bedrooms?
a) ¾
b)2/5
c)5/24
d)19/24
e)19/40
f)33/40
2. Suppose that the average length of passenger cars in the United States is 21.4 feet with a standard deviation of 1.3 feet and the car length is normally distributed. Then what percentage of these cars will be between 20 and 22 feet long? (correct to the nearest tenth of a percent.)
a) 2.3%
b)3.2%
c) 29.9%
d) 53.7%
e) 85.8%
f) none of these
3) An economic professor randomly selected 100 millionaires in the US. The average age of these millionaires was 52.1 years with a standard deviation of 12.3 years. What is a 98% confidence interval for the mean age, m, of all U.S. millionaires?
a) 48.6 <m<55.6
b) 48.9 < m < 55.3
c) 49.2 < m < 55.0
d) 49.7 < m< 54.5
e) 50.1 < m< 54.1
4) An Italian statistician wants to estimate the yearly milk consumption in her country. She wants to be 98% confident of her information to within 10 pounds. If the standard deviation is assumed to be 40.6 pounds, how many Italians should she sample?
A)45
b) 64
c) 90
d) 110
e) none of these
5) The average number of miles that 80 truckers drove in a day was 550 with a standard deviation of 50 miles. What is the 99% confidence interval of the true mean number of miles, m, driven by all truckers?
a) 534.2 < m < 565.7
b) 535.6<m<564.4
c) 539.0<m<561.0
d) 537<m<563
e) 540.8<m<559.2
f) none of these
Two statements, A and B, appear just below. Each statement is either true or false. A statement should be regarded as a false unless it is true without exception. Read each statement and then choose one of the answers listed below the statements.
- Extremly close (error less than 0.001) to half of the area under the normal curve is between z = -0.974 and z=0.674.
- Drawing an ace from a standard deck of cards is less probable than throwing two sixes with one throw of a pair of dice.
a) Only statement A is true
b)Only statement B is true
c)Statements A and B are both true
d)Statements A and B are both false.
7) A vending machine distributor wants to be 99.5% confident that the coffee machine is dispensing the correct amount of coffee to within 0.15 fluid ounces. If it is known that the standard deviation is 0.32 fluid ounces, how many cups of coffee should be measured?
a) 13
b) 18
c) 25
d) 31
e) 36
f) none of these
8) the average cost of living for a family of 4 in twelve different cities was found to be $65,351 with a standard deviation of $7711. In dollars, what is a 90% confidence interval for the true mean, m?
a) 62751<m<67,951
b) 61,353<m<69,349
c) 60,452<m<70,250
d) 59,301<m<71,401
e)58,438<m<72,264
f) 57,568<m<73,134
g) none of these
9) The average life expectancy of citizens in 27 randomly selected European countries was reported to be 74.8 years with a standard deviation of 2.6 years. What is a 99% confidence interval for the true mean for all European countries, m?
a) 73.947<m<75.653
b) 73.771<m<75.829
c) 73.560<m<76.040
d) 73.410<m76.190
e) 73.265<m<76.335
f) none of these
10) Fifteen different Thursday evening programs reported a commercial cost an average of $169,000, with a standard deviation of $81,000. What is the 99% confidence interval for the true mean, m, correct to the nearest thousand dollars? 302K is 302,000
a) 132k<m<206k
b) 124k<m<214K
c) 114K<m<224K
d) 107K<m<231k
e) 99k<m<239k
f) 97k<m<241k
g) none of these