All hypothesis test also require hypotheses as well as conclusions.

1. population assumed to be normally distributed has an average income of $75,000 and the standard deviation is $15,000.

A) What is the probability of randomly selecting an income from this population that is below $60,000?

B) What percentage of incomes would you expect to find between $70,000 and $80,000?

C) What is the probability of randomly selecting an income of more than $90,000?

2. A retail outlet would like to know the average age of its costumers. A survey of 100 customers revealed an average age of 35 years and the standard deviation is known to be 4 years.

A) Calculate a 90% confidence interval for the mean age of all customers.

B) Calculate a 95% confidence interval for the mean age of all customers.

3. A consumer group is claiming that ABC Concrete Co. is ripping off consumers by putting less than 60 lbs of ready mix concrete in its bags labeled as such. A sample of 36 bags revealed a mean weight of 59 lbs while the standard deviation is known to be 1.5 lbs.

Test the groups claim at the .05 level of significance.

4. A sample of 64 batteries revealed a useful life of 60,000 miles and the standard deviation is known to be 5,000 miles.

A) How long would you expect longest lasting 5% of batteries to last?

B) If we wanted to eliminate the 10% of batteries that last the least amount of miles, what batteries would that be?

C) The longest lasting 80% of batteries would be expected to last how long?

5. A builder of storage sheds claims that its sheds have an average area of more than 700 sq/ft. The standard deviation is 25 sq/ft.

A sample of 36 sheds revealed an average area of 705 sq/ft.

Test the builders claim at .05 level of significance.