1)Based on the model N(1152,88) describing steer weights, what are the cut off values for

a) the highest 10% of the weights?

b) the lowest 20% of the weights?

c) the middle 40% of the weights?

2) A livestock cooperative reports that the mean weight of yearling Angus steers is

1155pounds. Suppose that the weights of all such animals can be described by a Normal model with a standard deviation of 87pounds.

a) What percent of steers weigh over 1250pounds?

b) What percent of steers weigh under 1000pounds?

c) What percent of steers weigh between 1200and 1300pounds?

3)A consumer organization estimates that over a 1-year period 15%

of cars will need to be repaired once, 10% will need repairs twice, and 4% will require three or more repairs. What is the probability that a car chosen at random will need

a) no repairs?

b) no more than one repair?

c) some repairs?

4)A survey concluded that 40.4% of the households in a particular country have both a landline and a cell phone, 10.8% have only cell phone service but no landline, and

10.1% have no telephone service at all.

5) in a group of 20batteries, 4are dead. You choose 2 batteries at random.

a) draw probability model for the number of good batteries you get.

b) What's the expected number of good ones you get?

c) What's the standard deviation?

6)Assume that 9% of people are left-handed. We select 4people at random.

a) How many lefties do you expect?

b) With what standard deviation?

c) If we keep picking people until we find a lefty, how long do you expect it will take?

7)A waitress believes the distribution of her tips has a model that is slightly skewed to the right,

with a mean of $8.60 and a standard deviation of $5.60. She usually waits on about 50

parties over a weekend of work.

a) Estimate the probability that shewill earn at least $450.

b) How much does sheearn on the best 10% of such weekends?

8)It's believed that as many as 20%

of adults over 50 never graduated from high school. We wish to see if this percentage is the same among the 25 to 30 age group.a) How many of this younger age group must we survey in order to estimate the proportion of non-grads to within 4% with 90% confidence?

9)It's believed that as many as 21% of adults over 50 never graduated from high school. We wish to see if this percentage is the same among the 25 to 30 age group. What sample size would allow us to increase our confidence level to 95% while reducing the margin of error to only

2%?

10)An environmental agency worries that many cars may be violating clean air emissions standards. The agency hopes to check a sample of vehicles in order to estimate that percentage with a margin of error of 3% and 95% confidence. To gauge the size of the problem, the agency first picks 80cars and finds 12with faulty emissions systems. How many should be sampled for a full investigation? The environmental agency should sample at least

Nothingvehicles.